@Ratfink Connecting two sites with Wireguard VPN is absolutely doable, and you don't even need fixed IP's for it to work.
When you say you have 5 fixed IP's from your ISP, I'm kind of assuming you have your office at your house? Meaning they are both connected to the same fibre? Otherwise, if they are at very different locations, is it still the same ISP?
In terms of getting the IP's on the respective pfsense machines, I assume you know how or have instructions from the ISP to do this. Might be MAC based if DHCP for example...
Anyway, running pfsense on repurposed HW is very common and can be done "barebone" or virtualized. So you shouldn't have any problems getting to to work on your rack servers, hopefully.
So step one is of course getting both machines up and running. And since they will be for different sites and connected via VPN you must make sure to use different LAN subnets on them. Like 192.168.1.0/24 on one and 192.168.2.0/24 on the other.
Once you have them up and running you can follow a guide like one of these to set up wireguard.
Even though you have fixed IP's it might be a good idea to get two domains, unless you already have that.