Synology DS -> unRaid offsite backup

[fivechickens]

I have onsite (client) a Synology DS1813+ with ~15TB of critical data behind a NAT. 

Offsite (host), I have an unRaid 6.8.x server with two 10TB disks I've purchased installed in it (my Brother's house) plus access to his parity.

 

I've been looking at what storage options I have to create an offsite backup (w/ encryption and versioning) and I suspect using HyperBackup with the rsync client is the best option, but is it?  I first tried Syncthing and it doesn't appear to offer encryption.

 

My goals are: 

• reverse proxy on the offsite host similar to Quickconnect so I don't have to worry about its IP changing.
• host-side encryption so that the owner of the unRaid server doesn't have access to the data I store on it.
• versioning of the backup via the synology hyper backup client or similar
• little to no CPU impact on either side onsite or offsite.
• little to no hands-on management required on the host side outside of a docker for sftp or rsync.
• little to no port mapping.

Thanks!