Is an overwritten synced document gone for good?

There’s Arq, which can back up to different locations. It runs at selectable times in the background.

I back up with it to

• NAS folder (Arq mounts/unmounts it automagically)
• Backblaze (immutable)
• Microsoft via WebDAV

Paranoia, I know. But DT contains all my accounting information, so I can’t afford to lose anything from it. And I can’t be trusted to run manual backups regularly.