I know it's tricky to do sometimes, but really, just not getting grab baited is really important. As you may have noticed, shieldgrabbing is pretty iffy, and you can't count on it against Peach if she spaces her aerials correctly. Up-Bing is good in this matchup not just for followups, but for escaping stuff. The wind effect occasionally also helps keep Peach in the air, which is generally not a position she wants to be in for long.
Jabbing as usual is good. I felt when you actually were using it, things were going slightly better.
You were getting outplayed pretty hard on the D-throw stuff (and by the way, D-throw D-smash doesn't really work on Peach if I recall). I know it's frustrating when D-throw strategies don't work when you want them to, especially since successful reads for G&W can make or break the game for him.
If there is a Smash that I think you should be using more against Peach, it's U-smash. It does a pretty good job of protecting G&W's hurtbox once it's out, and it baits pretty well (F-smash is kinda not useful against Peach, given she outranges it with F-air).
And I dunno, it's not like you were playing bad in general, but you definitely were getting outplayed pretty severely when it came to spacing. Just like, in the heat of the moment, it probably was hard to observe, but there were some crucial decision points where you had to really know when N-airing or doing something else would have been safe against Peach's spacing, or for covering her landing/recovery options (which are really limited, although her ability to weave can be a bit tricky). So like, you just missed a bunch of potential opportunities to capitalize just because you weren't able to implement N-air as effectively as you could have.