@DimentioThere's a documented list of what actions do get you banned, and for extra safety you should set up emunand for offline modded play (which mimics telemetry of a unmodded console) and use your normal sysnand for online play. I don't think skin changes (aside from Switch menu profile pic changes) net a ban compared to piracy or cheating, though Nintendo can always decide to ban you for even harmless homebrew. I myself didn't set up an emunand so I assume my homebrew actions have been picked up via telemtery, but I haven't been banned and I've even bought DLC from updates while my Smash Bros. was modded.