I got the same exact setup with DT syncing over WebDAV on my Synology NAS, except for encrypting the Shared Folder that hosts the DT Sync Location, as I think if that folder is not mounted, you don’t get DT to sync with DTTG, and I use the app all the time.
But it’s good to read other people are using DT as a Password Database, as I do it as well.
Obviously, the weaker barrier is the sync in DTTG, as the files can only be protected by a Passcode (or Face ID) to access the app. But that’s already something.