I agree about the USB Ethernet dongle. Unless you only require short distance wifi range (eg hotel room temp router) the radio in the pi isn’t going to be enough

I built a pi4 router a few years ago, and it’s still running great, I recommend the project. But unfortunately I can’t find the HOWTO and it was before I started taking good notes. I assume your current router is a phone company supplied modem/router?

My setup is cable modem–>pi router–>switch–> old netgear router in Access point only mode

Being that your router/modem is upstream of router, I’m not sure if you could pass-through the WAN to the pi router, and pass back the LAN to the router/modem for the wifi… maybe someone on here can shed some light?