So just want to share my success.
Both houses have their own Debian server ZM KVM w/ passthrough NIC, ZFS RAIDZ1, pfSense, fiber iNET (100/40).
First setup was a ZM VM at her house, through OpenVPN-AS and record to my HDD, mounted to her VM. This worked but recieved a lot of null events.
Second attempt was to switch out OpenVPN-AS with Wireguard, this improved a bit, but still a few null events happening.
Final attempt, ditch the VPN, open up the camera port at her house through pfSense and lock both ends down so only our IPs are accepted, along with the specific traffic and ports etc. Add her rtsp to my existing ZM VM and bang, works like it was local.
Hope this helps someone trying to do the same thing.
My thoughts were, while it's nice to have cameras and record, a breakin can take a few mins and what happens if they take the servers? no data, so this is my cheap cloud solution. We record eachothers cameras remotely on eachothers ZM VM and if anything happens there is a recording captured allowing some peace of mind to help with insurance etc.
Each camera is rolling 25fps @ 160KB/s (approx.) @ 1080p, approx 8.6gb per camera per day. Night time drops to 4fps @ 50KB/s.