hardware requirements for POS

I have a client who has trouble with displaying my Unity standalone application correctly. It should run on a terminal with touchscreen and portrait resolution 1080 x 1920 Pixel. He currently tries several systems to check out performance and quality in order to find the lowest possible configuration with low energy consumption. (He would prefer to use an Intel configuration with onboard graphics.)
Now he reported that some of the tested configurations only show black screens or only a small part of the screen, even if running a smaller screen resolution. Please let me add detailed informations about this configurations later.

The hardware engeneers however have questions, that I am not able to answer. They are quite short:

  1. Is Unity a VMR or Overlay application?

  2. Which color format is used: Packed or Planar?

  3. Details as to when and why the Unity application chooses OpenGL over DirectX?

About the last question I already told “Unity always chooses DirectX if available, otherwise OpenGL”. But this answer seems not to be enough for them.

Does anyone please have any details about this questions?
I can request more detailed questions, if I would know what to ask, but honestly I have not heard about VMR/Overlay and packed/planar color format until now.

You can force Unity to use OpenGL with a command line argument http://unity3d.com/support/documentation/Manual/Command%20Line%20Arguments.html