Apparently, WiFi is spotty on OPNsense. I did start looking into home grown options, but WiFi 7 with 10Gbit ethernet is no joke. Most hardware ends up being power-hungry and noisy.
The Omnia NG is fanless, meaning quiet and power-efficient. It's also small and relatively stylish. The small hardware LCD is very handy, and everything Just Works. The whole package is just so well put together.
Fanless is attractive on paper, but often means overheating and unreliable in practice. A large, slow fan in a bigger case is always better if you value reliability and a long service life. The best 10G router that you can buy is a low spec PC with a two-port 10G NIC. Make sure airflow is directed to the NIC (a PCI fan bracket is useful for that). WiFi is best handled by a dedicated access point, ideally the ceiling-mounted commercial type.
In my stress tests, I've not seen any issues with overheating. My 10G ONU connects to the router over an ethernet cable, and the SFP+ module that plugs into does get quite warm, though not hot enough to be uncomfortable.