For one thing, Apple has a custom Dolby Atmos Implementation on their headphones that ties the accelerometers in the AirPods to detect head position and then adjust sound strength to places where you turn your head. Supposedly when watching movies with Atmos or 7.1 it's incredibly immersive. They just announced their new iMac with 'Atmos' (I want to see how this works) as well however. You probably could connect over HDMI as you state.
Yup. It’s like the fact that your eyes heck all over and I believe slightly vibrate in order to sample from slightly different positions to improve image quality.