Yes, that's correct. If you don't have sufficient disk space, then you may have to restrict what you backup to just the Home folders (what you call a "profile.") If you want another suggestion rather than using Time Machine make a bootable backup of the HDD to the backup drive using Disk Utility.
Be sure you erase the backup drive before doing the following:
Clone using Restore Option of Disk Utility
1. Open Disk Utility in the Utilities folder.
2. Select the destination volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Select the destination volume from the left side list and drag it to the Destination
entry field.
5. Select the source volume from the left side list and drag it to the Source
entry field.
6. Double-check you got it right, then click on the Restore button.
Destination means the external backup drive. Source means the internal startup drive.
This backup is a basic file by file backup. All files are accessible. You can boot the computer from the backup drive should you need to.