xzx covered it pretty well imo
Grab release stuff:
- Grab release leads to Up Smash or Nair provided there aren't any platforms for Wario to land on
- GR Up Smash at 85% should
not kill you on most stages, even if the Up Smash is fresh. Peach will want to go for about 90-95% to be safe (I prefer 100% just to be sure)
- Peach has a guaranteed GR Up Tilt on Wario regardless of whether there are platforms (depends on the height of them though but certainly for BF and SV this is true)
- I personally don't think the Uair string works very well on Wario in general so I'm sceptical of it working after a GR
You want to camp the **** out of Peach since your mobility is much better than hers
Once you get her in the air, try your best to juggle her as much as possible. I know Uair is a great kill move but it's also a good juggler so use it, use it, use it. You can get your kills from Waft, F Smash/F Tilt or edgeguarding. Bair is also good for suprise kills.
Fair is an excellent poker and forces her to face you meaning she can't retaliate with a quick Bair
Be vicious with your edgeguarding - even if you don't outright kill her, you can still harrass her and get her on the ledge. When she's on the ledge go for Uair if she goes for a jump get up or F Smash/F Tilt if she goes for a ground get up or Fair from the ledge
Peach's main tactic will involves trying to wall you out with Fair and Bair. If she whiffs her aerials, use your superior air mobility to punish. If she gets very careless with her spacing you can run underneath her and shield grab as she lands, Wario's grab is pretty decent imo. You can harrass her with Dairs but watch out for Up Tilt/F Tilt. DI up if she catches you with her Dair
Stage wise - avoid FD like the plague for obvious reasons. If you do somehow end up on this stage, use tires as much as possible to interrupt her approaches/Float since there's no platforms for you to dance around and do shenanigans. I also don't think YI is a good stage for Wario when fighting Peach but that's just my opinion. Take her to Lylat, everything else is fair game
This is a very tedious MU because the person who throws the first punch can often find themselves getting punished for offering up their hurtbox so consequently it becomes a game of baiting by throwing aerials out at...nothing
Be immensely patient and defensive in neutral situations but once you get her in an unfavourable position in the air/offstage, really go for it because getting the lead early on puts you in a very advantageous position
tl;dr Camp camp camp