Backup is stored wherever was defined storage directory. By default, this folder is xopero_repo. You can perform replication using RTRR - it is a remote replication service, which is provided by QNAP. Any information about RTRR can be found on QNAP's official website.
Real-time replication is also possible after adding another path in the storage edition. A description of how to do this can be found in this manual.