Can a Google/Samsung backup be restored if the account holder is not logged in? I am concerned about security on an old phone that I have given away, after resetting it.  Smart lock won't  make any difference, as it only applies to my home location.
You can remove the device from your Google account prior to factory reset with this link Google's Security Checkup Page  and for recent device removal have a look here Google's Recent Devices Page ... if none of these help then look at this for all linked devices Google's Support for Linked Devices