If you want to do only dialy backups, then you dont need mysql replication indeed. I thought you wanted to have a failover system with current data.
Regarding /root/ispconfig replication. This directory does not contain any data that changes after initial ispconfig install, so it has not to be replicated.
If you do not switch over the ip address to your backup server in case of a failure, you might have to change ip addresses in the website configurations as well.