Something I'm realizing that I've been doing too much of when I play vs most Foxes is not knowing when to retreat and wavedash away and just playing defensively. I'm too often trying to wavedash towards Fox and close the gap, where a lot of my moves just end up getting stuffed in the end. Sure the wavedash forward is a good idea to use, but only in moderation I feel. I feel like a really powerful and useful maneuver in neutral would be to dash forward to bait the Fox to come to you, then dash back, wavedash away, and turn into and ftilt, dash attack, grab, etc. I feel like perfect wavedash away is pretty underused and I'm pretty confident that it actually gets you out of the way of SH nair and even FH nair approaches.
I also can't stress enough how useful SH instant upair is vs Fox, even out of shield it's pretty damn good. I just gotta remember for myself to play more Defensively vs Fox and not always try to attack him. Having space on stage is pretty important, so Yoshi's Story makes this actually a bit more difficult, but it's still pretty doable on that stage. FoD too.