So, Fox's visual design. The direct claims it's from Star Fox Zero but it's actually pretty clearly a hybrid of Zero and his design in Smash 4.
It's based on and not entirely from Star Fox Zero:
https://youtu.be/L93H7YC-83o?t=405. Brawl and Smash 4's designs were based on Star Fox Command's which is the first game that started using current head style for Fox. Brawl added in the visible holsters for Blaster, Reflector, scouter lens, and greaves over different colored boots.
I am slightly confused as to why they didn't just use the entirety of Fox's Zero design (he even has the reflector!) though.
Probably because it would mean they would have to heavily remodel or make new models for Fox, Falco, and Wolf who can't really use his Brawl design anymore if they're basing Star Fox mainly on Star Fox Zero. Considering they have to work on +68 characters who even if they don't get new models, would be getting updates and polishing to improve on what they looked like on Smash 4, that's a lot to do and a lot of time that could have been spent elsewhere.
Fox in Star Fox Zero at least resembles and carries over traits from Command and post-Brawl, but Falco and Wolf look quite different. In Falco's case, his head, body shape, and fingers look different and Wolf's outfit, body, and head look different from Assault and Brawl to Zero which is based more on 64, but with Assault and Brawl's elements. So, the most they're doing for Fox and Falco are putting in details from Zero like the patterns on their jackets, new boots, and more textured fur and feathers, but they're leaving some things out that could be considered trivial like the Reflector designs form Zero, Fox's circle things on his collar, and their head shapes are more in line with Command and post-Brawl. Fox's is less notable, but I think his muzzle is a bit larger, fuller, and less "triangularly cartoon-y" and flat in the front in Zero.
Personally, I dislike Brawl, Smash 4, and Zero's outfit designs because it feels like there's a lot going on when there shouldn't be. Zero's is the worst in my opinion with all the random accessories and add-ons to their jackets. Some of it's cool like Falco's golden arm bands, but the grey, silver patterns and blue glow-y thing on Fox's collar are unnecessary in my opinion. They're over-the-top in an untasteful way unlike Bayonetta, Dante, or Sam Gideon's designs in their games. Sam's from Vanquish and his suit has all these cool moving parts which some of the recent Transformer games feature too. Command's outfit designs which are basically outfits from the first game to 64, but updated are my favorite because of how simple they are. If it were up to me, I'd go with those designs and only add in the holsters for Blaster and Reflector and the arm bands for Falco. The greaves and scouter make sense, but looking at Zero's rendition of the metal boots from the first game, they look protective enough that greaves aren't necessary. If anything, they make me question why they were given different boots and greaves in Brawl. As for the scouters, they look futuristic and would probably help by giving real-time info, but they're fighting on foot and those look dangerous if someone where to hit them in the eye. Maybe that's how Wolf lost his eye. Anyway, while piloting, you'd figure their Arwings would already have screens to give them info and are advanced enough that they could display additional HUD information if they need to pull them up. Scouters like those make me think that they should be used when analyzing things on foot and being retracted when they don't need them or are fighting or they're sneaking around like Snake with his Solid Eye in MGS4 or fighting at very long ranges where it's unlikely someone could hit them in the eye easily.