I use this bash script to replicate to a second rockstor. Uses native btrfs send\receive commands. Works well. I posted further details of this setup here. Yes can schedule script to run using cron.
As for monitoring, if you’ve set up Rockstor email alerts you’ll be notified when script finishes. Plus, in ssh, iftop gives a good graphical illustration of which network hosts your nas is communicating with. The btrfs process will be using cpu during replication.
Could add final line to script to run remote command to shutdown (shutdown -h now). How to power back up automatically is the problem (for me anyway - I won’t physically be at remote location).