Well, the modem has a RJ45 gigabit capable connector that connects to your router so that will work. The Orbi 960 however is 10GbE WAN capable, but you’re not gonna see those speeds on a ADSL/VDSL service.

A small rack and an ODF wouldn’t hurt.

Not much correct with that install. Wrong connectors mated, no protection for the incoming fiber cable or for the patch cable going into the house. A small bump on that patch and it’ll get smashed against that “tube” and break.

I’d say set it up on the OPNsense machine. It already handles all your firewall/NAT stuff so it’ll be easier to manage. With the wireguard service on the unraid, you’ll have two machines to configure.