I´ve been doing more testing in kinect. I continue thinking that the big problem for the kinect is that it wants to track the full body (skeleton API), and that makes jitters and erratic changes of position when you are seated. The fact that you have a HMD in your head doesnt help too, because the kinect thinks that your body starts just below of your HMD and does erratic movements too.
This could be adressed making a new SDK prepared to track faces with HMD´s and with the option to track seated people (like kinect v1 has).
This problem improves with distance, if you can put the kinect in front of you, with an angle near to 0 and with 1.5 m of distance, the track improves. But it continues making some erratic movements, less often but it does. Also, for placing the kinect as i said, you have to do a new space to use vr that is not in front of your monitor, so i dont know if it is a good solution.
Another problem is the lag. The kinect itself introduces some lag in the ecuation, and the fact it works at 30 Hz, make it some laggy. Dont expect to be as responsive as rotational track (in PIMAX or GEAR VR). You can live with it, but it present and rest inmersion.
For the opentrackkinect vs native kinect v2 driver4vr option, i much prefer the opentrackkinect because of the smothness of Accela filter,i know this introduces some lag to the ecuation too but i need that smoothness to play. Furthermore the opentrackkinect take the input of the skeleton API too so it has the same problems and does the same erratic movements that i mentioned.
Hope this helps.