OpnSense is a fork of pfSense - both are based on freebsd
ARM support is getting better there in BSD land - netgate/pfsense has funded development for ARMv7a and ARMv8a for Armada 38x and Armada 37xx chips, and has built private pfSense builds to support their products.
Looking at pfSense/opnSense, in comparison to OpenWRT - all three similar enough in capability and performance, and I can speak true to this, as I do have pfSense running as my edge router on my home network, and no problems with OpenWRT doing the same.
Upside to OpenWRT is that it can leverage things like Wireguard, as this is upstream, and very linux cenric - client options are available for Win/Max/iOS/Android in userland.