From the pit's side here is how it goes down for us against fox.
what each character has on the other:
Pit:
1. Chaingrab at the beginning can easily lead to 40%-50% lead right off the bat (you can also combo fthrows>fsmash if you don't have room for full cg).
2. even though neither really “outcamps” each other, Pit’s arrows **** fox off stage (although pit can force the approach by camping his reflectors since he has the better projectile).
3. Pit overall out ranges and outprioritizes fox.
4. Pit is pretty much the only one who will be getting gimps in this MU due to his vastly superior recovery.
5. Jab, dtilt and AR wreck shop near the edge and on stage when used right due to range, priority, and the ability to stop his phantasm (jab and AR only for this tho).
6. Planking>fox
Fox:
1. DJC (double jab cancel), Dair, and Nair all lead into true combos for damage and kills.
2. Fox kills us way earlier with his oh so reliable usmash (outside of gimps).
3. he is faster than us and his reflector stops camping to a certain extent (but there is always the threat of OHKO if they sit in their reflector).
4. He can gimp us on stages like YI and PK Stadiums (where we can’t go around).
Overall while this is a pretty much in pit's slight advantage because in this MU there are a few things which allow pit to generally win this match up both on and off stage.
ON Stage:
Since everyone knows the ramifications that CGs have in any match lets just focus on normal gameplay (however i would like to note that it leads to pit's pseudo 0-death). On stage jab and dtilt are going to be pit's main tools against fox and he will be using them a lot. These keep fox away from pit while constantly allowing pit to reset spacing but do the nature of the moves fox can't really do anything in retalliation to them. Also sh dair and just using fair in general is pretty effective as a mix up again due to range and priority over fox. Also juggling with uair, usmash, utilt, and throws are pretty effective here. In the air while our aerials over all outrange his none of his aerials under estimated by us pit's. Obviously nair and dair combo and such, his uair and bair are effective kill moves, and his fair can damage AND kill if used properly (however it is highly unlikely due to how easy that move is to DI). However our nair eats his aerial moves for breakfast and as stated the rest out range/out prioritize his. Also pit's fair is a great spacer and bair can used to get kills and gimps if he is offstage due to it's long lasting hitbox and the nature of fox's recovery.
OFF STAGE
A fox off stage is a dead fox when playing pit. While he can shine stall to help deal with arrows, the fact is when he uses a jump or recovery move our arrows shut him down. Also jab and AR both when held in the line of his phantasm stops him and his recovery in his tracks. Mirror shield reflects fire fox. If he is recovering from below a fast falled bair will gimp or stage spike almost every time. Whereas pit can just go under the stage if he is in even a remotely bad situation. also pit's planking destroys fox and it allows us to keep the match at our pace.
all fox has in this MU is kill power and speed to allow him to get in reads if pit messes up. that's how it is, pit has to mess up, otherwise, fox can't really get inside pit to do the damage.
Against DDD:
we can cg him up to 47% and until he is past 30% we can fthrow>fsmash him for plenty of damage. DDD has to approach since we greatly out camp him. our jab (and hell even AR at times) wrecks him since the infinite beats his spot dodge and eats his shield away. we can sh nair him and practically guarantee a shield poke with enough time to retreat afterwords or nair through him again safely. we are one of the hardest to cg because if he messes up even a frame our WOI will stop him in his tracks and allow us to retreat plus since it will be near the ground when activated it get's wing refreshed so that even IF he could hit us out of it offstage, we still have all of our jumps and recovery. while he is heavy, our frame 2 utilt, our dair, our dthrow, and his recovery make hitting him with our bair easy and it will kill him around 140%. our WOI can stop him being able to grab the ledge out of his recovery and it is actually possible to reflect his recovery by jumping into his falling *** with mirror shield (it's hard on timing, but i've personally done it). his jumps are easy to eat with arrows and we can chase him far offstage with relative safety.
juggling DDD is pretty easy and gets us a lot of damage, his waddle dees aren't even a threat camp wise compared to arrows, and our multihit moveset beats him down. that's the MU in a nutshell anyways.
ill wait for a response before i talk about falco and oli (i have a lot of falco experiance as well as fox, olimar i am taking all the other pit mains' word on it because i don't play the MU enough)