The procedure for restoring from backup is explained here Frequently Asked Questions (FAQs)
The channels backup is necessary when you open new ones or close ones. That backup file will save the “status” of your channels and will close them in case of recovery procedure, moving the funds you had in them into your onchain wallet.
The seed for your Umbrel wallet is the one you should keep it safe and use it to restore in case of SHTF.
Optional you can use that seed into Bluewallet to import your onchain wallet and manage the funds.
1 Like