I haven’t looked into matinee’ yet so my current plan is to use a two player mode and have Player2 basically being my custom camera with animation imported from Maya. (though you might not want to have animation as you want to do green screen?)
I have not yet tried this at full resolution but I should be able to severly degrade my own vr-playing quality settings and hike up the ones on Player2. As I have only one computer. If you have two then it should be easier to get good quality and performance.
EDIT: Of course you would have to match your P2 camera to your real life camera maybe by taking measurements of position, angle, lens etc of the real life one and try to match this.
I had some plans to try and use an extra tracked hand controller taped to my camera to be able to move the camera around. Not sure if I will get around to that though.