I don't know if you still need advice lol, but I'm a Pika main. I'm not very good yet in Pm overall, but I do know some pika tricks. Most of the time you want to cancel your QA with an uair/utilt, but you can cancel it in practically anything you want. If I want to start a combo or a juggle I QaC into uair. If my opponent is on the ground and at a high %, I QaC into back air on the ground. Sometimes I try to apply some pressure or disrupt them with QaC into fair, but most of the time it's just uair or bair. You can also spam QaC into QaC (and so on), but I don't recommend it unless you're trying to get to the ledge as fast as possible. Otherwise, you'll likely get predicted. A very fun option to do is QaC into wavedash. You can use it to play mindgames in neutral (QA towards the opponent, wavedash away from him, Fsmash or something) or you can use it to land really fast one a platform without any lagg. What I have been learning recently is combining all those QA options with ledgecancels. Pikachu can get extremely fast and intimidating if you QA into ledgecancel. You also should try to QA into ledgecancel if your caught off stage, it's a very fast recovery that gets you right back in neutral. I tend to prefer stages with platforms because of it, especially battlefield. Don't use it too much though, it's quite risky. Actually, don't spam QaC overall, it's way better to use it as a surprise attack or as some kind of recovery.
As for matchups, I tend too have trouble with characters who have a huge disjoint. Especially Marth is a tough matchup because of his disjointed sword. What you want to do especially against those characters (but because of Pika's awful range actually most of the characters) is use your speed and thunderjolt to bait a laggy move. you can punish it with qac--> uair and start your combo.
I think pika has a good MU on fastfallers.I think Pikachu does quite well on captain falcon. On stage you're at a disadvantage, but as soon as you get him offstage he is practically done. QA to hug the ledge. If you think he's going to make it on stage, fall below him and tail spike him or bair him into oblivion. If you don't think he's going to make it, just hang there
Reverse down b off stage is also quite nifty for edgeguarding.
Overall, you want to focus on gimps if you play pikachu. Use tail spike, bair, footstool or QA from the ledge to disrupt their recovery. I've taken stock from players who were way better than me just by standing on stage and QA into ledge hug right before the oppent tries to sweetspot it. Most of the time they don't expect you to make it in time to the ledge, so instead of landing on stage they will fall and lose a stock.
I'll leave it at this, I hope this helps. have fun with pika ;D
