New XPS 17 NVIDIA graphics question

@jemsurvey1  The default behavior is that the Intel GPU has direct control of all outputs and the NVIDIA GPU when needed operates as a "render-only" device, doing all of the hard work and passing completed video frames to the Intel GPU for passthrough to the display(s).  This technology is called NVIDIA Optimus.  The determination of when the NVIDIA GPU is needed is somehow made by Windows and the NVIDIA drivers.  It tends to work quite well since the technology has been around for years now and is by far the most common way for modern dual GPU systems to be configured, but if the NVIDIA GPU is failing to activate when an application that requires it starts or activating when it shouldn't be, NVIDIA Control Panel can be used to customize this behavior.

On the XPS 17 in particular, you have another option.  There is a setting in the BIOS to make the NVIDIA GPU the primary GPU, which cuts the Intel GPU completely out of the loop and gives the NVIDIA GPU direct control of all outputs, including the one driving the built-in display.  This allows for some technologies that don't work through Optimus (VR, G-Sync, Adaptive V-Sync, stereoscopic 3D, technologies to run certain high-end displays), but it means the NVIDIA GPU remains active all the time, which will impose a battery life penalty and might result in increased heat and fan noise.  I can't quantify those for you though, since I don't own an XPS 17.

The MacBook Pros you're referring to I believe have the Intel GPU controlling the built-in display (with the NVIDIA GPU operating as I described originally) and have the NVIDIA GPU directly controlling the display output connectors, with no ability to configure this.  In that case, the NVIDIA GPU has to remain active whenever an external display is active, even if nothing graphics-intensive is going on.