Not sure about Breez, but I know Muun has backup, just not in the typical word format most are use to. I've tested to make sure that if I uninstall and reinstall, inputting my backup, that I can access my funds and it works fine. The main issue I have with Muun is that sub swaps are dependent on on chain fees. It "acts" like lightning, but as soon as you try to send someone sats when ordinal junkies are flooding the mempool, you become a believer in free lightning channels lol