My issue seems to be resolved, but a few things changed so I'm not sure what fixed it:
1. I added a *dedicated* router for the Quest, tplink AXE75/AXE5400, as a 6GHz access point.
2. Meta seems to have pushed a small update that improved Airlink performance and turned on a few features, even though I'm still showing v57 in the update/version screen.
I can now run Airlink with dynamic bitrate set to 200Mbps with only the occasional dip in quality.
So now I have the following (somewhat ridiculous) setup:
1. Asus AXE7800 as main router, servicing general devices and uplinked to cable modem.
2. Asus AX3000 router configured as access point, uplinked to the 7800, with one VR PC wired to it, and running a 5GHz band in the DFS range just for my roommate's Quest 2.
3. Tp-Link Archer AXE75/AXE5400 as access point uplinked to the 7800, with my VR PC wired to it, running just the 6GHz band at 160MHz width just for my Quest 3.
However.. it works, it's reliable for Airlink as well as Virtual Desktop, and the quality is excellent.
