Hoooooo boy. I don't know where to even start.
Well let's start with game 1.
First off your opponent is really really bad. You're better, but still not all that good. You roll waaaaay to much, a better player could have punished you badly for that.
Definitely work out the habit of rolling.
You also missed many many possible punishes, like when Snake whiffed the Fsmashes or Sspecial.
Now for game 2
Again your missing punishes. When his Nspecial missed you and you were still close to him you could have capitalized on the recoil he had.
Now we have a player better then you, but still not that good. You never punished on the trips, rolls, or anything like that. You didn't tech the D-throws.
It's hard to comment on the videos, because the play level is so so low. x_x
Character specific things however;
As Squirtle you should be use your other aerials more as that are all rather good. Fair is a good move but so is Bair, Uair, Nair, and even Dair are all good aerials, so you should be mxing them up more. Definitely be in the air a lot with Squirtle. Also the lack of utilizing Shellshifting for Shellslinging, Shellstalling, and Hydroing made me sad. Also, you don't need to use Usamsh to kill, or even go for it, though using it as a hard read or punish is still good, as Fair can get the kill a lot more reliably, which is another reason to use his other aerials more so as to not let it get staled out. When Squirtle tires out don;t try to get the kill, just keep racking up damage or change out.
As Ivysaur, Nair and Bair a lot more while Uairing and Dairing less. Don't use Usmash or Fsmash as much. Dtilt more. Space Ftilt correctly. You spam Razor Leaf a bit too much, try to use it smarter. You kept trying to go for sweetspot Uspecial, focus on other things first as this isn't Project M to where you can combo into it >_>.
As for Charizard. Nair isn't that good. Fair and Bair are the main aerials you want to use. Uair is good for juggeling howeve. Jab isn't that good. Dash attack is horrible. Ftilt is decent. Utilt is great for anti-air. Dtilt is good. Fsmash sucks, you have way better kill moves like Bair and Dtilt. Usmash is good though and you used it rather well. Dsmash is good for punishing dodges. Don't whiff Sspecial so much.
that's all I got.