I find with Peach that it's fairly easy to read her, because of how easily Fox can react to the situation. If she's being defensive, you can either laser (depending on distance) or do what I do and just activate super technical beam and run in, don't miss l cancels and **** with shine and grabs. As soon as you get her in the air, bair is ****, and up smash either beats or ties with all of her aerials. Again, if she's being really aggressive, up smash out of shield is really broken. I dunno, I don't find peach as threatening as I used to, mostly because you beat her with combos, you beat her with priority and you beat her with options. I find the best approach to peach is actually not camping, but to be very aggressive. Look for up smash and grab opportunities. This matchup is really about having a good push-and-pull game, so if you can land your kicks and grabs, and can think your way out of her tricks (because her punishment game is good vs Fox), then it's your game.
EDIT: People were asking about Falco earlier, and I mean...you could go on forever about possible strategies for getting around them, but there's never an easy way through things in this game. You just have to think. Jump over their lasers, whatever, but if they start using up tilt, just stop using aerials because that move beats all your aerials. Punishment comes easily, since Falco gets comboed like he's your ***** once you get a shine or grab.
Honestly, all you can do for now is watch and react, and try to think of a way to get out of the pressure. There are no answers in words, because it works differently for everyone, but it will come to you.
EDIT2: There's one more thing I should say here, and that is to address the myth that Falco has control during the match. The only thing he has control over, in truth, is whether or not he approaches, and there's nothing you can do about that.