Jitsi allows to use their server by default and don't need to install own, but if you like to use your own it is possible.

As far as I see from documentation communication is encrypted and only talk's participants and video bridge has access into the channel. Video bridge it is server through which all users are connected. It means that Jitsi server encrypts the communication, but decrypts it on server side and if you set video bridge on your own server, your security guarantees will be roughly equivalent to an end-to-end encrypted call.

Also p2p calls (between two member) are not decrypted with server side and you have end-to-end encrypted call even if you use jitsi server.