EDIT: Been playing with it a bit now and if it uses keepass as the DB the advantage I see right now is that having it in Nextcloud means automatic sync, and there are several autofill and syncing apps for various OSes and password sharing and automated checks for breaches. It's probably a better option for anyone with Nextcloud than going the Keepassxc/syncthing route.
You can encrypt the entire vault and all the contents,... but imo, that should be a default setting.
Seriously, as-is, you log into Nextcloud, click on passwords and every password is literally right there. I'm sure they're encrypted in the database but fffff.