You already have a good understanding on how to play the neutral as M2 in my opinion.
Game 1
A little too much dash attack. It has benefits at low percents, but it's easily punished on shield which is something you have to avoid.
I could be mistaken as the last time I played a Pikachu was last Friday, but i think n-air is a good option to deal with quick attack (not that this pikachu used much of it, just something to take note of). If i think they're going to quick attack into me and i'm willing to risk it I go for u-smash (just don't try running u-smash against Pikachu, he's too small). If you're trying to punish a Pikachu who has used b-air or something that makes him crouch during the landing lag, grab usually won't work. If this happens use walking d-tilt.
You could convert a bit more damage off your d-tilts with f-air and DJ u-air > f-air/u-air at mid percents, it's good to retreat if you're not confident you can get the hit though because if it whiffs, you're in a good range for Pikachu to start his combos.
1:24 - Going to the ledge is a good option against fast opponents. If you want to land on stage, try falling in one direction then teleporting behind them or platform cancelling a teleport.
1:58 - From the ledge, the best ways to get off the ledge in my opinion are
- neutral get-up
- tap away > side-b towards the stage (use against people shielding at the ledge)
- drop down > dj u-air (use against people waiting at the ledge/charging an attack)
- jump > airdodge (because of M2's ability to move while airdodging, it's hard for an opponent to punish the jump recovery option if they are unable to hit you before you airdodge
- jump > dj > shadow ball/disable (over time, opponents often adapt to M2 at the ledge by moving a bit away from it, thinking they're safe to run in and grab/attack, so this can be used to try and punish that)
the attack option was ok, but just remember M2 will probably get KO'd if they shield it and smash attack.
Game 2
Past 40%, I suggest you stop using dash attack against Jigglypuff as on shield it sets up for an easy rest
Because of M2's big frame you have to be careful about them rolling into you and misspaced aerials putting you too close to them. I think you played this match well however - teching/rolling away from Jigglypuff is usually the safest option as she is slow.
In summary, less dash attack, more conversions out of d-tilt and try out the alternative ledge getup options and using teleport to mix up where you land. Stay determined, your style doesn't need to be changed, just added to.