I said before that I don't care about tier lists. I just want to know another character that I'd might enjoy if I enjoyed Meta Knight.
I'll still give my opinions about them, I guess.

- I have no idea how his Up-B works, so I probably won't get very far with Pikachu. Though I think the reason why I wouldn't use him is because I hate Pikachu. I don't know why, I just do.

- I don't think I'd ever get used to Bayo. Her recovery goes against everything I've ever learned as a Smash player.
It has nothing to do with tier lists. They're both just "competitively viable". You said you liked to be competitive so I thought about good characters in general and these are the two I'd consider good, fun MK secondaries. Though, considering your main problems with both seem due to their slightly awkward recoveries, I think calling yourself competitive in the OP, in any sense, is a little misleading...
Still, I would've probably recommended Pika and Bayo even if you weren't looking for competitive characters, but oh well.
The only other character I can maybe think of you might like is Falcon (Can rush down, has a good grab game, combos, etc. Much worse offstage than MK, but unmistakably faster with that same feel of Bait/Punish overall.).
MK is a weird character in that he's pretty unique in his toolset (Combos, great recovery, grab game, high pressure moves. Honestly, I think Pika
is the closest you'll get.). He's just missing a few good ones, so finding a character like him or that can compliment him while still being fun for people who like MK is kinda hard.
(But as an aside, I don't play Pika much, but I used to hate Pika too before I really got into playing them in Smash, so I can kinda understand. lol)
Sorry for the slight change in subject, but does anyone know how well fox stacks up as a secondary for metaknight?
Fox would probably be pretty good, but he's a totally different character overall so jumping between MK and Fox could be a little jarring. He's got a very good arguably rushdown style, but most of his tools are good for hit and run, too. His combo game is far less reliable IMO than MK's overall though. They're basically incomparable IMO, but IDK, someone more knowledgable might be able to draw comparisons between the two you might like (They're both kinda fast I guess?).
However, by all accounts, Fox takes a lot of practice like MK, and is mostly solo viable. So at that point, you might as well just main Fox so you're not straining yourself. lol