I just wanted to confirm - I can backup Qubes on my machine with a password; move those backups to another machine with a different Qubes and restore there with only the same password. The various passwords/phrases and login user/password used on boot and login from the source machine are not required for restoring and using the backups on the 2nd machine?
Yes. You encrypt your backup with some password, and then you can restore it on a new machine with Qubes, which has a different dom0 user and different disk encryption password. You only use the first password to decrypt the backups. This is actually how you upgrade to a new release or migrate to a new machine.