Battlefield 4 doesn't use Phsyx… not sure about Shadow of Mordor. All I know about SoM is that they are boasting your going to need some serious hardware to play it a high settings.
You can disable the 2nd GPU in NCP but it will still draw idle range power... which keep in mind is pretty low. There's probably a more complicated way of turning it off through your BIOS
This article does seem to be pretty nVidia biased, but it does illustrate how a dedicated GPU makes a big difference with phsyx:http://www.volnapc.com/all-posts/how-much-difference-does-a-dedicated-physx-card-make