I dont know much about your router/ap, but from some light googling the virgin media hub 5 has 2.5gb/s ethernet and wifi 6 which should be fairly decent. I agree with what most comments are saying about connecting the pi using ethernet ("hardwiring" it) and setting a static ip. The raspberry pi image flasher even has an option for that in the advanced settings if I'm not mistaken. If youre worried about not being able to plug a keyboard/mouse and monitor to the pi look at ssh. If you arnt comfortable with command line/terminal I cant say I'd recommend setting up your own router/firewall.
If you dont have any ethernet ports available on your router then looking at a good switch for 2.5 gbps might be a better bet, I always perfer physical connections to wifi.
If you do want to jump down the rabbit hole of pfsense/opnsense/openwrt then hit ebay and look for a cheap workstation and an intel nic, that will get you started messing about with it. Be sure to do research about power consumption of the device youre getting, the raspberry pis sip power but beefier machines will suck some power and might show up on your electricity bill.
I use opnsense, the forums are a good place to look at hardware that you might want to gravitate towards, intel nics have been my best bet but there are plenty of resources to tell you what is compatible and what isnt with openbsd.