Vaults and backup
What a vault is
A vault is one file. Your documents, folders, tags, and notes all live inside it, encrypted, in Apple's standard disk image format. The file has the .docucasa extension and it's yours. It sits on your disk like any other file and it moves like one too.
Backing up
Copy the vault file. That's the whole procedure. Lock the vault first, then copy the file to an external drive or let any backup tool you already use carry it. Time Machine works too. Just know that the trustworthy copies are the ones made while the vault was locked. Test your backup once by opening the copy in DocuCasa. A backup you've restored from is a backup. Anything else is a hope.
Where to keep it
Any folder that isn't cloud synced. iCloud Drive, Dropbox, and their kind copy the vault's inner pieces one at a time, and syncing an open vault can corrupt it — the vault itself, not just the copy. And be careful here. If your Mac syncs Desktop and Documents to iCloud, your Documents folder counts as cloud synced. A backup is a different story. A locked vault doesn't change while it uploads, so a copy of a locked vault is safe to keep in a cloud drive. Lock the vault, copy the file there, done.
More than one vault
You can keep several vaults, each with its own password, its own Touch ID setting, and its own startup folder. Home and business, yours and a parent's. Switch between them from the unlock screen.
Moving to a new Mac
Copy the vault file to the new Mac, install DocuCasa, and open the file. That's the entire migration. Nothing to export, nothing to rebuild, nothing left behind.