Aoi Yui
If you struggle with reaction times, that would probably knock off some of the characters who create confusion and mix-ups using items (they're particularly good when it comes to the kind of playstyle you referred to). Characters like Mega Man and Pac-Man make amazing use of rapidly dropping items in mid-air and catching them again (and other item-based techniques), but there's a hefty amount of input required as a result. However, there are a couple you may want to try out who make use of items/projectiles that can't be picked up, and they're great for catching your opponent off-guard playing the way you described.
- (I've mentioned Villager so many times here now, people are probably so sick of me, but hear me out, please! D: ) If you haven't already, watch some of Ranai's matches. While it's a shame to miss out on his/her smashes if you can't get them right consistently, there are plenty of tools available here, and the inputs required have a nice flow to them; not too rapid. If you play it right, people won't know what you're thinking, or what's coming next!
- This is a real oddball... Working on Duck Hunt can be mentally exhausting for some, but the pay-off is that fighting a good Duck Hunt can be mentally exhausting for your opponent. Not really input heavy, but definitely takes a steady amount of mental input! Haha.
There's a lot of strategy to be had using his can, from creating a double amount of stage presence to giving extra damage off of throws. You can actually manipulate the can in all kinds of ways using his various attacks, as well. He's quite campy (can do great stuff once he has an opening, however), and like Villager's tree, he can hide behind his down special, which helps when you're in a more projectile-based match-up.
- Does require good use of his down throw combos (there's also an optional up throw combo at 0% that's great for heavies, but the inputs are more rapid and dependent on reaction time), so I'd check those out first before considering him. Otherwise, he can manipulate the opponent quite well (down tilt and up air can send people floating upward or suspend them in the air), and it's hard to know what to expect. His projectile is unpredictable. On heavies and fast-fallers in particular, you can go for down throw to judge at low to mid %s for a devastating 9 (good to know how the other numbers affect the opponent so you can follow up).
- May seem predictable, but Dedede actually thrives off of people expecting him to do one thing, and then reacting with something else, especially taking his gordo into consideration. You can change its trajectory, and if you learn how to space it, counter any attempt of your opponent to send it flying back in your face. Also, if you bait the opponent into getting hit by the gordo from behind, you can follow up with another attack while they're flying toward you. While there are legitimate uses for Dedede's smash attacks, since they are all pretty laggy and he packs a punch in general, you wouldn't want to be using them often anyway (down smash is probably the safest, but calling it safe would be so off). His tilts are actually much more versatile, and can wall out the opponent as you plan their punishment.
As always, it's a great idea to check out the official board for a character you're interested in to really get an idea of all they're capable of pulling off.