After some digging, it turns out that my motherboard, being a very new Alder Lake offering, has some bugs that the manufacturer has not worked out yet. One of those is issues with PCIe bus speeds.
According to my research, dialing the PCIe bus down to 3x seems to resolve a variety of issues all of which I had been experiencing, from non-working GPU risers (which caused me to return and replace two different SFF cases) to spammy nvme / AER errors. That change also seems to have made my audio issues dramatically less obvious if not completely resolved.
While I thought I noticed a couple of brief dropouts even after that, I also changed session.suspend-timeout-seconds to 0 in the bottom section of /etc/pipewire/media-session.d/alsa-monitor.conf as that seems to come up commonly when looking into audio sink suspension in pipewire. It’s hard to quantify the impact of that change, but over the last couple of hours of intermittent gaming and usage involving audio, I haven’t noticed any more dropouts.
There are still a few lingering issues which at this point I’m inclined to write off as caused by bleeding edge hardware for now. Gigabyte is on the hook for another BIOS update or two and we need another kernel or two under our belts. That said, I’m going to leave this open for a little bit before marking it resolved, in case anyone wanders by and has some useful advice or additions for this case or similar ones.
Let my struggle be a reminder to future people that running Linux on hardware that was released mere weeks prior and expecting everything to execute perfectly is sure to result in some hand wringing and head banging.