Yes, and it does work if you do not define/create a peer (just the upper part with the private key). The QR Code was somewhat smaller if i reckon correctly and it passed the servers private/public key pair. That's probably not correct. The private key should never be exposed i guess. And as i added a peer the QR Code didn't work anymore (syntax error in peer).
No, not tried yet. Will test that next time.
Edit: 'reload' didn't help but 'restart' shows the new public key now on 'wg'.