I was concerned that I'd run into this issue when upgrading, but so far almost everything is working for me. In case it's helpful to anyone else with similar hardware:
Unraid version 6.7.2 with PCIe ACS override set to Both
Mobo: Gigabyte AX370-Gaming K7 (F42a BIOS)
CPU: 1700X upgraded to 3900X
I have 2 Windows 10 VMs with a variety of passed through devices.
VM 1
r9 390 with VBIOS. This is the primary GPU.
Also passing through an NVME SSD
VM 2
Radeon 7850 without VBIOS
The above worked with the standard 6.7.2 kernel, but I did switch to the custom kernel here in order to get sensors working:
I followed the process here to upgrade from BIOS version F6 to F42a: https://forum.level1techs.com/t/solved-bought-x470-aorus-gaming-5-wifi-bios-update-recomendation/145836/9 The post on the thread was for Gigabyte x470, but it turned out the same process works for x370.