PC gaming connected to home theater questions

Hey All -

I have a Windows PC set to boot up and launch Steam Big Picture with an Xbox controller. Works really well. I'm wondering how I should connect the system to my AVR.

Assuming I have a AVR that supports HDMI 2.1 so I plug it into one of the AVR HDMI ports from my HDMI 2.1 output on my video card. Then how should I set up my audio settings in Windows or my games?

Does it pass PCM? Can I get 7.1? Can I get Atmos? I have a 7.2.2 setup.

Thanks!