Hi,
ok, I do not understand how you want to transfer records from one user to another user using BF, because, if you use BF you can store records in the database but if you use Content builder then you can manage with the submitted records.
If some other users leave the site, you can block that user in the database that in the database '_users' in column 'block' replace value '0' with '1' then the user will be blocked. Or you can create an account for that new users in joomla backend->Users
Or if you want that other users use the same id as the old user, you can change in table '_users' column 'username' and you can generate a new password and insert it in column 'Password'. But do not change ID of that user only username and password! Then user With changed passwords and usernames can access to the site!
I hope I explained it well!
If you have more questions, feel free to as!
Regards,
Mirko