I rely on Bitwarden (slooowly migrating from… a spreadsheet…) and am thinking of keeping a master backup to be SyncThing-synchronized across all my devices, but I’m not sure of how to secure the SyncThing-synchronized files’ local access if any one of my Windows or Android units got stolen and somehow cracked into or something. I’m curious about how others handle theirs. Thanks in advance for sharing!
Bitwarden has an import tool. You should be able to convert your spreadsheet into the format they like and import relatively easily.
For backups, you can create encrypted backups through bitwarden. So it shouldn’t matter if synching itself is a secure process as what your syncing is already encrypted.