How do you play against link with:
Marth/Roy
Jiggz
Ness
Squirtle
C. Falcon
Falco
Charizard
I have a friend who I can beat easily in every matchup except when he is playing link. Link is literally his only good character. However, when he plays link, he usually wins. I would say he wins 7-8 out of 10 games against me regardless of who I play against him with. I have found the most success with Falcon/Squirtle despite neither being my mains. I can sometimes win with Marth/Roy only because they are my mains. I have no idea how to approach with jiggz despite jiggz being my secondary. I have yet to try Ness against him as I just recently picked up ness. And my Falco/Zard usually get 2 or 3-stocked despite both being some of my best characters.
He usually walls me out with projectiles and when I can get close he uses his spin attack, nair, or Up smash to cancel out my approach. I've tried approaching both on the ground with dash dancing/wavedashing/wavesmashing, yet he cancels this out easily with boomerang/arrows and when I do succeed in getting close on the ground he just shields and up bs or nairs out of shield.
I have better success approaching in the air because it dodges the projectiles, but when I get close enough, he can easily up smash, up tilt, f tilt, or shield me and if I do get a hit off, the boomerang hits me on the way back.
I have tried swatting the boomerang while approaching but I have limited success with this and he almost always has an arrow followup or sometimes a bomb followup.
My most success has come from approaching with squirtle's side B or short hop bubble (since it comes out at an angle), and C. Falcon's Falcon Kick. However, all he has to do for squirtle is down tilt the shell or shield the bubble into Spin attack. With falcon if I only approach with Falcon kick it gets predictable and he can punish me in multiple ways so I have to do arial approaches as well which has the problem from above involved.
It seems like he has an answer to everything I can dish out at him. I am a better overall player with the rest of the cast than him and he doesn't utilize any of the ATs in the game like glide tossing, wave dashing, L canceling, ect... so it is very frustrating to consistently lose against just his link. I just don't know how to deal with his link. Literally no other matchup against him is a problem so I think I just have trouble vs link.
You need to learn. Pay close attention to what he keeps doing when you do something, and then punish him for it. Bait moves out. Link is a very risk for reward character. That means that if he throws out something like the spin attack and you block it or it misses, you have an opportunity for a large punish.
With Marth, he has an extremely good Fair which is extremely good for swatting Link's projectiles away. Keep your proper spacing and Fair away. Keep in mind the Marth has a down tilt that can actually poke through Link's up b when he is using it to recover. This sets up for a cleaner edgeguard. You can rising Dair punish a Zair tether attempt as well.
Roy is similar to Marth, juggle Link in the air and stay on him. Edge guards are crucial as Roy. Also remember not to use your jump right away and side b to stall first to gain horizontal distance. Roy has a bad recovery so be careful. Spacing is done carefully and keep in mind that all his sweetspots are in the center of the sword unlike Marth who has a sweetspot at the tip.
Falcon is good if you stay in Link's face. Link is the perfect weight to get combo'd. He's actually the same exact weight as Captain Falcon. Stay on him and work off of hard punishes. Falcon Kick is extremely good. Nair beats projectiles if spaced correctly.
Squirtle is good because he has super armor until he is at high percents when he is shell shifting(side special). He just goes through whatever hits him for the most part because of his super armor on the move. Squirtle is also small and quick. This makes it far easier to weave through Link's projectiles and hit him before he can get any more projectiles.
Falco is literally Link's worst match up. His lasers cannot be clank shielded by Link while in his fast walk animation by the Hylian shield. Falco is good because he is incredibly fast and is good with applying pressure. Link struggles against pressure. If you have a tight pillar combo on Link he'll have a tough time moving. He can only Grab, Spin Attack, or Wavedash out of shield. These options when compared to Falco are extremely slow. If you are pillaring and he attempts to spin attack, you'll be above him where there is no hitbox for the attack so you can continue pillaring. Falco shuts down Link's projectiles due to how fast his moves are. Short hop laser approach stuns Link or forces shield which allows Falco to shield pressure him like crazy. Be warned that if you get grabbed by Link, say goodbye to your stock. Link has incredible punishes on spacies if he takes their jumps and they're in the air. Down throw>spin attack is guaranteed on fast fallers which all of the spacies are. This sends them off stage and Falco basically has no recovery. It's awful. So offstage Link can edgeguard Falco quite easily.
Jigglypuff struggles in Project M in general due to how ridiculous the recoveries are in the game. In Melee Jiggs could edge guard opponents because they didn't have outrageous recoveries. In Project M it's insanely difficult to edgeguard with Jigglypuff unless it's on a spacie or Roy In my opinion.
Ness struggles against Link. PK fire is good for combo start up with Ness. Especially of the Link doesn't smash DI. If you hit PK fire you have a guaranteed combo follow up if the Link doesn't smash DI. Ness gets Down throw Down Air killed quite easily. Boomerang also destroys him.
Charizard is pretty solid in Project M. In order to optimize him you want to he sure to sweetspot ALL of your moves. This means hitting them with the fire ember on the tail for most of the moves. His Nair goes through platforms and the stage near the ledge. This makes for great edge guarding against tether characters. Nair is amazing. Seismic toss(up throw) is very good on stages with low ceilings and platforms. Hit them on the platform at high percents with up throw and you have a guaranteed kill. He can also mess up Link from below with tilts and smashes. Down smash as a tech read on platforms is amazing for combo potential. Charizard has a difficult time getting down if he is in the air above Link especially. Link can Up air Charizard pretty hard. Basically try and maintain center stage and get Link above you.
If you want my advice, instead of constantly changing characters, stick to one or two. Learn the ins and outs of them. Learn the match up. Ask your friend what he's constantly doing that you don't notice. If you want to improve you must try. Don't constantly switch characters.
Also, Link is an incredibly strong character in Project M. Don't be down on yourself if you're losing to him. Learn his bread and butter combos and how to avoid them! I hope some of this helped you!