After buying a GTX970 and a PCI-E16x to PCI-E8x cable, I startet the journey to flawless gamestreaming from unraid VM (Win10) to my living room (Nvidia Shield TV). But after hours of configuration work with graphic settings, EDID override (no 1080p 60Hz option in monitor EDID file) and Moonlight settings , I got somehow frustrated that there were still hickups and stuttering in video and audio. There was a 4ms latency signalled by moonlight, but driving a racing sim with a racing wheel (directly connected to the server per 10m active usb cable), I could clearly feel and see that there was a latency of at least 200ms.
After thinking it through again, I set up my VM xml file to passthrough the second NIC on my motherboard, deactivatet the network bridge in Win10 VM, and all problems gone! It seems you have to use a physical NIC to use the gamestream feature, at least it solved all problems in my case.