Ultimately I wanna run OPNSense since that’s what most people recommend.
Why? From your description it doesn’t seem like you need it. You’ve a small / normal network and OpenWRT will provide you with a much cleaner open-source experience and also allow for all the customization you would like.
Do you have any hard requirements that requires you to have the router and AP in separate devices?
If you don’t I’ll suggest you have a look at the BananaPi BPi R3 and here as it is a very good option with a 4 core CPU, 2GB of RAM Wifi6 and two 2.5G SFP ports besides the 4 ethernet ports. There’s also an upcoming board the BPI-R4 with optional Wifi 7 and 10G SPF.
I thought I thanked you for this at the time, but it seems I didn't. Sorry about that. This post has been invaluable to me and has coloured how I've been aiming to build out my network. Thank you so much!