There is a lot to unpack here! I was not aware until recently that vyos had never made the switch to fq_codel away from pfifo_fast in the first place. We long ago (in openwrt) ripped out support for pfifo_fast entirely, and it is the default now in most of the main Linux ecosystem due to being more general purpose than sch_fq.
Before I dive into arguments, (can you engage those on the bug? Viacheslav? Is that how I do that?) The best defaults for a router OS, particularly one targeted at powerful hardware, should be BBRv3 and CAKE. Second best would be BBR and fq_codel. nearly last would be the combination of sch_fq + BBR, which is in a couple demonstrable ways worse than pfifo_fast + cubic!
What I have always encouraged however is experimentation so folk can more deeply understand congestion control problems more intuitively. These days I tend to recommend the crusader tool, coupled with packet captures, and then to look at the RTTs in Wireshark. There is also flent. Normally when I post to forums I get censored by putting in links, but I will do that in my next post.
I (perversely) love that y’all have made this basic change to the core OS and propagated to your userbase as it will be so much easier to demonstrate what damage you have just done to network performance overall!!!