Strategy for file/image backup

I wonder what is the best strategy with current urbackup server (linux + btrfs) and windows desktop client (with CBT driver).

since I want to give user the ability to restore files, so file backup is a necessary. and I don’t count on users can set up/use the backup path correctly, so I need to backup the whole drive.

for disaster recovery, I need to do image backup. but since I already backup all the files, the image backup waste time and space.

when I really need to recover a windows desktop, I need to recover from a image backup, but the newest files maybe at file backup.

I think ideally if user can restore files from image backup(currently only administrator can mount image), or administrator can do disaster recovery from file backup.

in reality I think since disaster recovery in seldom, maybe the restore cd can optionally restore from one image backup + one file backup. so I can backup only one or two image backup and many file backups.