North-South will definitely require solid switches given all of your Management, VM Network and vMotion traffic will be going through it but the requirements for those should be exactly the same as any other server solution (HCI, traditional SAN etc).
I can only see PFC being a requirement if you're using the same switches to push the storage traffic across, or presenting the storage directly to other hosts on the network. In that circumstance though, I'd probably just opt for physically separate switches.
That said, these are all assumptions.
The only HCI solution I've worked on (albeit very closely) is Cisco Hyperflex.