It is possible to set the default in the ACP but uses can override it in their settings.
Making the USER page private
Any way to make the USER page private and not readable to guests? Currently, anyone may go to the USER page and read all that user's posts for a prvate forum.
Hide user list and data from guestson in
/admin/settings/userand hit save. You should also remove find/read privileges from guests if you don't want them to see content.