I myself have been working on my own character's matchups, and haven't gotten Fox in yet. Here's my current progress that I have typed in my document, and this is in the view of a Pit-to-Pit conversation:
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Matchup: Fox
Intro: One of the faster characters in the game and is capable of pressuring if not careful or familiar with Fox much. One should know what to do quickly since fighting against speed can be frustrating, so having some nice reaction times and knowing what to do will help in this matchup.
Range/Priority
Both the characters have similar ranges at times, Fox's F-air seems to have some interesting priority, where Pit still has some of his disjointed attacks, F-air and F-tilt being 2 of them.
Angel Ring can be outprioritized by a carefully-spaced F-smash, and F-air to the best of knowledge.
Weight/Power
Fox is one of the lighter characters (7th lightest according to the Wiki) which benefits Pit's poor KO power (even with his F-smash and sweet-spotted B-air). Fox's better KO moves include his F-smash, and his infamous and powerful U-smash, which is one of the best vertical KO moves known in the game.
Camping
Both characters have a projectile and a reflector (well, Pit has 2 reflectors). Let's take a look at Fox's gear:
-Blaster
A blaster that shoots lasers at such a rapid shooting rate, The lasers do little damage and does NOT make the opponent flinch. A Fox can shoot 2 shots per short-hop, in a similar nature like Falco's SH, but doesn't flinch opponents and has less range, but at the same time, faster to perform since Fox falls faster.
If a Fox is just shooting blaster on the ground (which hopefully is something a Fox wouldn't do), you can reflect it with Mirror Shield, or shoot an arrow at him before he has time to block it.
-Reflector
This reflector comes out quickly and protects Fox from projectiles on all sides. The reflector does damage when it first comes out, and when the opponent is super close. It seems to have invincibility frames too.
Overall, Pit's the better defensive one, not to mention having a superior ledge-camping game. Hitting Fox can be difficult, however.
Speed
Fox is the 3rd fastest runner, after Falcon and Sonic. For attack speed, Fox does have a nice amount of quick, spammable moves, such as U-tilt, D-tilt, F-tilt, and Down-B (especially when he's airborne).
General Basics/Strategies
Okay, since Fox is fast, expect to be pressured quite a bit by his speed. Some of Fox's tactics can include using multiple U-tilts when the opponent is as low percentages. The U-tilt knocks the opponent in front of Fox, where the foot is moving towards. DI in that direction where you are being knocked towards (again, where Fox is facing), and upwards to avoid getting hit by a lot of U-tilts.
Fox's jab is mediocre, of which it tends to allow many characters to put their shield up quickly in-between hits. It is just better to DI away from it if the jab is used.
Pit can perform a CG or F-throw to stutter-step F-smash of your choice. It's strange considering how Pit can CG most heavy characters, but no light ones. However, the F-throw CG seems to work on Fox (perhaps 3 F-throws maximum) probably because of how fast Fox falls. Pit MIGHT have a chance to do 2 F-throws before doing a stutter-step F-smash if he is fast enough.
This is only if the Fox is at 0%, and a normal F-throw to stutter-step F-smash does around 29-30% damage regularly, depending on how stale the moves are.
Being directly below a Fox may NOT be a good idea. Many Foxes like to use their Down-B to slowly hover down, and mess up your timing to attack. When you're vulnerable or when your attack is over, the Fox can come on down using D-air, which has a chance to go through Pit's U-air depending on how angled and parallel the moves' hit-boxes are. Pit's U-air can hit if he isn't completely below where Fox's D-air hit-boxes are considering that Pit's U-air hit-boxes are kinda wide horizontally.
Anyways, speaking of Fox's D-air, here are some D-air follow-ups for Fox:
-D-air > U-tilt
This can be uses at decent percents like 40%+ or just enough percent so the opponent will be stunned enough so they can't shield the U-tilt
-D-air > Grab
A substitute for the U-tilt, where Fox can choose to grab opponents in case they think their opponent may try to shield it, but still leave themselves open for a grab. Most Foxes use D-throw more frequently.
-D-air > D-smash
This can be used to push opponents off the stage depending on how much damage they have.
-D-air > U-smash
The big one, used when opponent's in killing range. It's pretty much no way to escape it when caught in it, and have a good enough damage. As if that wasn't bad enough, D-air has a chance to make opponents trip. Try to avoid this the best you can.
Sometimes, if you can predict when Fox is gonna stop hovering with Down-B, you can strike him with an angled U-air, or wait and dodge the D-air, then quickly do a U-tilt. You can punish D-air after shielding (not Mirror Shielding) it.
Fox seems to have an interesting pivot grab. When used with the C-stick somehow, Fox slides with his pivot grab. It may have something to do with Fox's speed.
Edgeguarding/Gimping (Pit to Fox)
Pit has a harder time gimping Fox compared to the other 2 space animals. Here's what Fox has on recovery:
-Midair Jump
It's just a basic jump. It doesn't go that far, not to mention that Fox falls fast, so that pretty much degrades its use.
-Midair Jump + F-air
This is a substitute for the regular midair jump. When Fox uses the midair jump and F-air really quickly afterwards, he gains a vertical boost from the F-air. It can be hard to deal with with F-air's 5 hits coming rapidly with decent attack range. This outprioritizes Angel Ring.
-Side-B
Doesn't launch out as fast as Falco's, but still is fast and basic. You can edgehog this easy as long as you don't get hit by its hit-box, and if he doesn't make it to the platform.
-Down-B
This can also be considered "hovering" when in the air. It's when Fox uses this move constantly in the air to stall in the air, which interrupts your timing if you plan to attack. It can also reflect projectiles in the right timing. Even if Fox is hit, he can quickly do it again afterwards.
-Up-B
Outta the 3 space animals' Up-B moves, Fox's has the longest distance. It is still easy to edgehog it if the Fox decides to. The Fox may use it more often if he doesn't have his midair jump and is below the platform ledge.
Pit will have hard times trying to gimp a Fox. Sometimes, just shooting arrows at him may pressure the Fox, and depending on how many options he has left (hopefully he doesn't have his mid-air jump). You can Mirror Shield Up-B if you want (a Fire Fox going completely vertical will not change, except just turn the other direction Fox wasn't facing), but it's easier just to edgehog the move.
When Fox is on the ledge, aside from the basic "ledge attack" and options, Fox can drop down, and use his midair jump + F-air to rise up with those 5 quick hit-boxes, capable of going through Angel Ring. Predicting the height of where Fox will end up can give you a small chance to counter, but watch out for the hit-boxes, as said before.
Edgeguarding/gimping (Fox to Pit)
Fox technically doesn't have much ways to gimp Pit, but you must be cautious. Fox has a few things to use against a recovering Pit. Since Fox's blaster can't make Pit flinch, he has to resort to melee-based attacks. Against a Pit that tries to recover high, Fox can either use his jumps + U-air, or even his jumps + F-air. Remember that the Midair jump + F-air thing gives Fox a nice little vertical boost. The last hit of the F-air sends the opponent upward and has a chance to kill if Fox is high up there + the opponent's damage.
If Pit is recovering low or mid elevation, he needs to watch out for a Fox B-air, which is a good potential KO move, which sends opponents more horizontally.
Also, if Pit is forced to use Up-B, AVOID being close to Fox as much as possible. The Fox could use his reflector to knock Pit outta it with no problem. This makes it dangerous and don't recommend approaching the ledge IF Fox is on or close enough to the ledge where he can "shine" Pit away and knock him outta his Up-B, causing him to lose a stock. It doesn't matter if Pit is right by the ledge waiting for Fox to leave the ledge, for Fox's Shine still will get Pit before he can grab the ledge.
Overall, avoid being close to Fox, and don't approach the ledge if Fox is close by, or risk getting shined and losing a stock just like that.
Stage CPs/Bans
This information may not be absolute, or completely correct.
CPs
-Frigate
The right side of the stage when the match starts... There is no ledge to grab on to. This makes Fox's recovery there more weaker with no ledge to grab on to.
-Lylat
The tilting stage seems to mess with Fox's recovery more than Pit's, not to mention that Pit can fly under the stage to the other side.
Bans
-Halberd
As much as Pit is able to "Shark" the platform when it is in the air, it is easy to get a vertical KO here since the blast boundary is quite close, and therefore allows Fox's infamous U-smash to kill much faster than usual.
-YI
This is Pit's worst neutral anyways. Shy Guys block Pit's arrows, and Pit can't fly to the other side of the stage since the stage won't permit it, limiting Pit's recovery options.
Synopsis
50:50 even
The matchup is tough especially for those who are not completely experienced in the matchup. Where Fox's speed and pressure, not to mention trickiness meets Pit's disjointed attacks, relatively high defensive and recovering capabilities, and own pressuring methods.
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This is all that's in my document atm. And sorry bout the format. It looks better in the document I have. If anything is missing bout Fox, let me know.
As for a few things to know, I believe Fox's D-air can go through Pit's U-air if you are directly above Pit, but if Pit is not directly below you, where Pit's U-air and its somewhat horizontally wide hit-box is still around, Pit may be the one to actually outprioritze.
Against Pit's recovery, if you are ever to force Pit to using Up-B, and if he's going for the ledge, hog the ledge and just Shine him. You should have enough time to do it even if Pit is right at the ledge waiting to grab it, or at least in my experience.
Idk what else to put, but know that the Yoshi's Island stage can benefit you. This is easily Pit's WORST Neutral, as those Shy Guys will block Pit's arrows at times, and Pit can't fly under the stage, limiting his recovery options.
Anyways, I hope this helps in some way, but also, I would like to talk to some decently good and experienced Foxes (hopefully not biased ones) so I can discuss this and get the Fox's point-of-view on the matchup.
You can get me on AIM or PM me here, so I can discuss this a bit more. I'll appreciate the help, Fox players, and for now, I hope some of my information helps, and again, if anything is missing or wrong, let me know. I look forward to improvements in my matchup guides, and thanks in advance.
Pit 
