Talking defaults, Rosalina is pretty straightforward. Luma has some jank, but it's consistent jank. If we study her hard, we could probably would definitely figure out every single thing about Rosalina before Rosalina players figured every single thing out about Pac-Man if it came to that.
If it came down to sides hiding stuff, I'd be more scared of us. I mean, who else would figure out the little tricks that we do?
Rosalina has her moveset loaded with disjoints. Luma is Luma. They've got separation gimmicks, that's about it.
Pac-Man's arsenal of tricks has no end.
Also, I tested Rosalina jab at ledge roll distance away + Luma jab at the ledge. As expected ,we have an answer. Luma's jab combo ender will not hit Pac-Man when he's holding a ledge. If they do this to you, charge Key and chuck it at both of them when you get a chance.
Also, from the best testing I could do by myself, I find that our Bair is pretty good for challenging Rosalina and Luma in the air as long as you come in purely from the side. The halos will mess you up, but our Bair is considerable and wins trades with her nair and fair. I'll try to test her Bair tonight.