Well, my Little Mac is a bit of an opportunistic punish type, where I try to get in there, while still being patient and not too predictable. I also try to utilize LM air game. Many a player doesn't expect it, and LM does have some good combos that arise from his aerials. (Take for example, his dair lock, or his nair Maciside. true, you can recover with a footstool from the ladder, but if you have 2 stocks, and your opponent only has one, why not just suicide and take him with you?). Simply put, I try to find a good balance between a bum-rush beat-down Mac, and a patient, defensive type Mac. I also have counters for people who try and do nothing but grab me and throw me off the edge of the stage. As for Pac-Man, I try to play a bit of a barrage game. I frequent his lower tier fruits as spammy projectiles (cherry, strawberry, orange, and apple.) from there I can usually get in some dash attacks or tilts. Constant fire hydrants are a must too, both for punishing and for launching at players. (But again, don't be too predictable.) Paccy boys up b is good, but I tend to use his side b for a safer recovery with more K.O. potential. Lastly, his Galaga and Key are good for juggling and K.O.ing opponents.
*edit* zoning is also a must for both characters, but that can be said for all characters.