Multiple people can log in to accounts on a single Apple TV, and you can set up your app so each member of a household can use it with their own Apple TV account. When a user logs in, your app can access their preferences and GameCenter and iCloud data . If your app is also available on iOS or iPadOS, a user can pick up where they left off on their personal device as well.
Syncing with iCloud Drive is currently limited to a single user on the Apple TV, and that is the ‘Default’ user. However, if you’re using a media server like Jellyfin then there isn’t much need for syncing with iCloud.
To elaborate on my answer above, Infuse does not currently support the idea of multiple profiles in the app. This is something we have seen some interest for, and hope to explore for a future update. The thread linked above is the best place to keep an eye on for updates.