So, from looking at your videos, you're a decent Pac-Man player, but you have some bad habits and some notable weak point in your play.
In particular, you need to:
- Improve your defensive play, using traps and projectiles more actively.
- Improve your neutral game, particularly your shield game.
- Use punishable/laggy options more mindfully.
- Trade less with opponents.
- Stop pushing situations when you don't need to.
- Use Pac-Man's tools to their full potential.
Pac-Man as a character is one that is best played in multiple styles - he can be played purely offensively, defensively, or trap-based, but he really shines when he uses all of those playstyles unpredictably. Looking at your videos, you are playing Pac-Man purely offensively. Now, you don't do this badly, per se, but there are often situations when it's better
not to play offensively when you're using Pac-Man.
Defensively, Pac-Man is very slippery, being able to stop opponents from approaching with the tramptoine and hydrant, and being able to attack from far away without fear of damage. This playstyle is very effective against opponents which lack projectiles, are not able to do much damage without being up-close, or which struggle to do damage in the air or which are more ground-based. Aspects of this playstyle should always be used when you feel pressure and need to reset the situation to neutral.
One key thing to look at for this playstyle is that Pac-Man has a wealth of options against shielding opponents (which you will see a lot of, especially if you're throwing out oranges like you should be). When you predict an opponent's shielding in place, run up and do one of the following:
A: Up-B
B: Grab (Regular and turnaround are both options)
C: Drop a Hydrant
D: Throw a melon
E: Shield
F: Do nothing
G: Attack
A and B are the most reliable of these options to use, and both of them allow you to manipulate the positioning of a shielding opponent. Know that Up-B is generally more reliable than grab, as a missed one still isn't so slow that your opponent can punish you off of reaction. That said, C is a fantastic mix-up to use, as it pushes an opponent to the side and messes with their stage position without taking them out of shield; normally, they'll respond by rolling, trying to take out the hydrant, or attacking OoS, all of which can be punished.
E and F are baiting options. Often, when you run up to a shielding opponent, they'll roll, spot-dodge, or grab out of habit, which you can punish. Shielding, however, can be punished by grabbing OoS. Likewise, doing nothing (in preparation for a roll, spotdodge, or grab) can be punishes by attacking OoS.
G is the worst option to use, but the one I'm seeing you do the most.
Do not attack a shielding opponent unless you out-space them. Against a majority of the cast, Pac-Man can only poke shields by using projectiles, particularly orange and melon.
D is a trick with the melon. Throw it out, then run up to the opponent, who will shield (if they don't, then you can follow up). Then, when it bounces off their shield, jump and airdodge to catch it in your hands. It's probably the most reliable way to grab a high-level fruit outside of just running and dash attacking to get the Galaxian.
Recognize that your opponent has all of those options except for Up-B, Hydrant, and Melon when you shield, and use yours with that in mind.
You and I are in agreement that Pac-Man's grab is good, it seems, but you need to be very careful in throwing it out. Likewise on your smash attacks; if using a slower move is going to result in a trade, go for a faster move instead - the damage isn't worth it.
Another thing to note is that you don't need to pressure opponents when you're ahead. Let them come to you and make the mistakes; if you defend a specific area and let them approach, you'll find that you're getting damage in regardless.
As others have said, figure out some more tricks with Pac-Man if you can. Go into the Training Room itself and practice things. It helps. A lot.
Overall, I think it's your fundamentals that are lacking more than anything else. Improve those, and I think that you'll see some notable improvements in your play.