Actually, I didn't have any careful planning when I started out self-hosting Vaultwarden. I didn't even have system backup (was just a script kiddie back then, didn't even know about 1-2-3). I have to migrate my instance 3-4 times. But because I'm just hosting Vaultwarden for myself, I can export the whole account from one of the Bitwarden clients (either the extension or mobile app) and reimport it in the new instance. Because I always have at least three devices with active use connected to my Vaultwarden instance, for me this also counts as 3 off-site backup that can be used to re-instate the whole setup.

It is surprisingly very durable and maintenance-free even for a script kiddie like me to maintain. My advice is (at least when it comes to Vaultwarden) don't think too much about this, just selfhost it, at least for yourself. You'll probably be able to manage it when something happen.