there is an officially purchasable app on the Xbox store called "My Files Explorer" that also has full access to the whole file structure of the Xbox. it is on the store for years already and is even a paid app which costs about 3 bucks.
so if that is an issue, they don't really do anything about it lol. in fact said app is basically your alternative to using the FTP app in the OP
NES, SNES, GB, GBC, GBA, Master System, Genesis, Dreamcast, PS1...
basically, anything that is less taxing than Dreamcast will run fine on One S and even some Dreamcast games will run absolutely fine.
PSP should run well too
only PS2 and GameCube will give you issues