I find Peach's sordid KB on Dsmash to be fine, mostly. More KB on it won't really help unless it's a TON more. I'd rather see it do modestly increased damage per hit. 6, 7, or a pattern of 6 and 7s so that scoring multiple hits with it is somewhat rewarding. I've always seen it as a damage/safety move, and I don't think it really needs to do more than that.
If there's one attack that I can see needing fixes, it's Toad. Peach falls very quickly when using this move from the air, making an offstage use suicidal. The spores can also be canceled by the very same attack that triggered it, so making them unclashable would be nice. It also doesn't put the target into hitlag when triggered, so they can wind up running through her before the spores hit. Dunno if there's a fix for that, but it's another annoyance.
Peach Bomber could maybe use more KBG. That would be a "great and unique" kill option which is obviously not an easy hit for the angle it sends.
Her Fsmash could use more KB in all forms. The tennis racket in particular has an oddity where it has a "strong" sweetspot that has knee-like intensity. Normally though it hits pretty weakly and could use some consistency in power, considering the Fsmash object itself is randomized.
I think Peach plays fine, even with her overall lack of kill power. The damage she can rack up from the start is so good it makes up for it.