Well now I am on the trail of trying to disable Optimus... and it looks like it might not be possible on my Dell XPS 15Z. :\ I tried disabling my Intel Chip on my device manager, and that pretty much breaks everything. Resolution is dropped to 800x600 - and I'm guessing its not GPU accelerated.
Going to follow up with NVidia.. man its really going to suck if this a dead end for my machine, after all this work!
AFAIK, you cannot disable Optimus. Intel's GPU is the only way NVIDIA's GPU can communicate with a display.
Nsight (and PerfKit, as Nsight relies on it) really had a problem with Optimus, and probably it still has (I haven't tried the latest version yet).
Btw, you should know how to activate NVIDIA's GPU in your application.
By default, Intel's GPU is used. Fortunately, it is so easy with Optimus.