Well, you have two different subnets. I'd say a WireGuard-based S2S is one way to go. You'd be limited to the Beryl AX's 300 Mbps over WG but you can set a policy on the latest firmware versions (v4.8.x) to direct any traffic to the NAS on either end over WG. (This won't work with TailScale)
If you want 'raw' speed you're going to want to set up a mess of port forwards to whatever (both) side's services are running on the NAS(s) given the current configuration is a double NAT (on the repeater's side).
Slightly older screen shots but still relevant for S2S: