I'm not particularly familiar with Unifi products, but I'll throw out some thoughts in the hopes that they are useful.
What I do for Wireguard access to my home network is I have a Raspberry Pi with Raspbian and I used "PiVPN" to set up my own Wireguard server. It automatically sets up all the appropriate firewall rules and everything.
On the note of you being able to access one feature but not another after disabling remote access, it could be that your Wireguard clients are being detected as "remote" clients based on their IP scheme. For example, my LAN IP scheme is 10.1.1.X. My Wireguard clients however, aside from being routed through my PiHole, have a different IP scheme of 10.208.192.X . Therefore, even after setting up PiVPN with the proper firewall routing, I had to adjust the firewall rules on my other devices to allow incoming connections from that IP range. You may have to do something similar.
