Linux IOMMU Hardware, Good Groups Before Purchase

Hello Linux/IOMMU/QEMU people,

I am looking into doing a Linux system with virtualization and hardware pass-through. I have checked that the boards I'm looking at support both VT-D and VT-X in their manuals but have a few other questions that you won't get from manuals.

OS:
Kubuntu (I like KDE Plasma Desktop)

Hardware:
CPU Options:
Intel Xeon E5-2620v4
Intel Xeon E5-2630v4

Motherboard Options:
Asus X99-E WS/USB3.1
Asrock X99 WS

GPUS:
GTX 770 2GB Linux
GTX 1070 4GB Windows 10

Questions:

  1. Will these motherboards have issues with IOMMU grouping? I am more worried that the ASUS board will be a problem due to the usage of PLX chips. Is there a good way to know if the board your looking at has good IOMMU groupings? The block charts don't always tell the whole story.

  2. Does Linux Support USB 3.1? I think it does but which kernel?

  3. Will I have problems using 2 NVIDIA GPU's or will I be fine just black listing the pci-stub? (I already have these)

  4. I think Asrock board will have issues with BIOS not being pre-update for Broadwell-E (v4) chips, what are my options?

If anyone has better board options or hardware suggestions please don't be shy.

Thanks!