Hello trduff,
Sorry I'm really confused about your question.
The display export is executed by the Intel card, while you are able to set the games to be executed my Nvidia card, then transfer data to Intel to export, there is no conflict about this.
And about Windows Mixed Reality Ultra, do you mean something like below link?
Windows® Mixed Reality 體驗由 Radeon™ 和 Ryzen™ 提供It is supported by AMD while FX516 is an Intel product. May I know where did you see the advertisement?
FX516 does support VR, you may see that headset other than this HP ones work.
Thank you.