If you got the automatic updates on the bitwarden clients, they will show an empty vault if you are selfhosting vaultwarden.
It seems to be an accidental bug in the bitwarden clients that are assuming that they’re talking with official servers
It’s fixed with the latest release of the vaultwarden server that was published a few minutes ago
Yes they can both be used at the same time, though KeyPass stuff is new and beta. I’ve never used it.
There is both a subscription model and a one time payment model. I bought it with the one-time payment. I believe it was $15. But don’t quote me.