Limitations on Linking
The link between a user and a Nintendo Account can be removed at any time. After the link has been removed, the user can link to a different Nintendo Account.
A single Nintendo Account can be linked to multiple NX systems. When multiple NX systems link to the same Nintendo Account, the user nickname and icon is synchronized across systems. However, the applications save data is not automatically synchronized across systems. On the other hand, it is not possible to either link multiple users to the same Nintendo Account on the same NX system, or to link one user to multiple Nintendo Accounts.