From what I was reading though, TCP congestion control will do nothing on a router, as its only controlling how data is sent over a TCP connection established from THAT machine. So about the only use on pfSense would be if you were using OpenVPN over TCP.
In my own testing, it doesn't impact downstream traffic, it improves a servers ability to quickly reach and maintain optimal transmission speed. This is why it was such a great thing for Google as it optimised their servers performance.
BBR was relevant for my LAN because I have a NAS, so it improves the speed pulling data from that NAS (by using BBR on the NAS), or sending data to it (if BBR is used on the client).