It seems like it will help if your motherboard doesn't already have convenient IOMMU groupings.
There's nothing to indicate that this will help with the NPT issue, so expect poor performance (CPU or GPU, your choice).
There's nothing to indicate that this will help with the NPT issue, so expect poor performance (CPU or GPU, your choice).
There's also a thread on the vfio-users mailing list and on a few other mailing lists as well as some discussion on /r/vfio.