Thanks for this very detailed info regarding USB ports and the IOMMU groups. The Zenith II and Aorus Master were the two boards I considered as well, so this information is spot on for my needs. I pulled the trigger on the Zenith II due to integrated 10G and better USB options before finding this thread, just waiting for the CPU to arrive (probably tomorrow).
Just one quick question I cannot seem to find an answer to:
The Zenith II has the Asus "DIMM.2" connector on board, which supports two PCIE4 x4 M.2 drives. I was under the impression that those were connected directly to the CPU, w