Hello,

They will ban only your alt account as long as you go through registry and remove any traces from xboxapp.
This includes doing it BEFORE you decide to cheat on alt account. You can swap between them while cheating, but again, only after deleting traces of xboxapp id through registry.
However, as for bans, it's been undetected for a very long while now, but of course keep in mind it's not undetectable. There is always a risk of getting banned, especially playing obviously with the cheat.