Love it! I just recently started using Syncthing and may implement what you've outlined here.
As a fellow paranoid, what mechanism are you using for the separate backup?
Likewise. SyncThing and suitable file based databases allow so many instant 'cloud' solutions! KeePassXC across 5 devices with instant updates!
On the odd occasion it's been modified on two devices without a sync and SyncThing produces a sync-conflict file, a simple "Merge from database..." within KeePassXC happily pulls in the newer data from both databases to merge them again.
I use the Staggered File Versioning feature on at least one device + a separate backup mechanism to satisfy my paranoia about losing the database.