The first real virtual reality solution. It uses two or three external recievers to track head movements. Currently I am not sure if I move to the Oculus RIFT S, this second generation uses build in cameras and don't neet two additional USB ports.
If you need glasses you can use them under the Oculus Rift. Only the comfort is no good at all. I ordered this in my strength an am happy with it. They just click into the Rift and stay there, until I got guest flights.
If you fly VR, you cannot easily look at things outside the VR-headset. For this I copy my actual sequence into the image inside the plane (where existing).
Really helpfull is, if you put one important funktion in each sim on one of your buttons of your stick: Center the view to straight forward. On my hotas stick I use the button 7, that is the lowest one on the handle. You can center the view with the touch controllers, yes, but normaly I do aerobatics with hands on control.
Leap Motion is a small sensor to track hand movements.
I used this sensor before the rift but needed to program the interface to FSX. It was working in the way to popup a small window with the control focused.
There are solutions for combining the VR Glasses with the Leap Motion controller mounted. But since the Rift is using hand controllers I don't see the immediate need.