This question came to me in bed while I was thinking about ReHIPS!
Firefox allows one to have several user profiles. How does ReHIPS determine which Firefox user data profile to copy when the relevant checkbox is checked in settings?
By the way, this is a theoretical question because I only have one profile in Firefox.
ReHIPS works with physical files, simply copying them. I guess different profiles are either kept in one file, different sections or different files, adjacent folders. So I believe all user profiles will be copied.