Thanks again!
I googled "SR-IOV Hyper-V NIC security" and slight variations several times but not a single hit on the first 2 pages was about security, all were about performance. Do you have any pointers?
This is the best article I have found so far https://blogs.technet.microsoft.com/jhoward/2012/03/21/everything-you-wanted-to-know-about-sr-iov-in-hyper-v-part-8/ but it only mentions SR-IOV security flaws rather than it improving security.
Also, I found out that I can check whether a NIC supports SR-IOV via
Get-NetAdapterSriov
even though all NICs say that SR-IOV was enabled successfully, only the 82576 actually comes up as supported.
As for IOMMU, I am still not sure. Yes, the hardware components support it, but the BIOS also could disable it, and there is no such option on the Dell, also, googling came up with mixed results.