The X470 Taichi groups look pretty much in line with @AcidzDesigns Fatality K4 groups; probably not surprising given they’re both ASRock boards.
Since posting this thread, it’s become apparent that decent IOMMU groups aren’t the only barrier to a successful VFIO build. I’ve been following your unknown pci header type ‘127’ thread, and the current situation for both X470 and X570 seems to be less than ideal. I’m not adverse to manually patching/compiling kernels, buy would rather avoid it if at all possible.
Allegedly ASRock will be releasing BIOS updates for X470 boards in the coming weeks which contain AGESA Combo-AM4 1.0.0.4. Potentially something to keep an eye out for.