Q:

FPS drops sporadically, with Gsync turned on, even with just one cube in the scene

Problem has been ongoing for quite a while. ( more than 3 months, can't remember exactly when, sorry)
If I move the mouse outside the current part of blender framerate instantly shoots back up - for instance if i move mouse cursor from "3D viewport" over to "properties", for instance. 
Frame drops are down into the single digits. 
If fps drops while in 3d viewport, rotating the camera also makes FPS go back to normal (until it happens again)
FPS drop is not only happening when using the main blender window.  It can also happen when I have "blender preferences" window open. 
I use blender for modeling for 3d print, so I only use the modeling workspace.  I most often work on simple models. 
I use Solid mode Viewport Shading most of the time. 
If I play a youtube video/twitch/netflix on my secondary monitor, while working with Blender, FPS drop does not happen. 
If I turn Gsync off, the drops does not happen.  The drops do happen regardless if i have Gsync turned on for full-screen, or for both windowed and full-screen. 
The reason this is a problem for me is because when the fps drops happen, the 3d viewport especially looks like it's getting a few shades darker gradually.  It might also be a trick of the eye as a few flickers are going on, which irritate my eyes. 
Anyone have an explanation, or better yet, a solution? ( if it is possible to turn off gsync for just one app that would also be nice, but I haven't found anywhere I can set that up)
System:
Windows 10 Home
16GB ram
gforce gtx1660 (6gb) newest drivers, as of typing. 
Primary monitor is gsync enabled, but secondary is not. 
blender and OS is on a SSD, but blend files are saved on a hybrid drive. 

A:

Yes it's possible.  Go to nVidia Control Panel > Manage 3d Settings > Program Settings. 
Add Blender under Select Program To Customize.  Changing to the following settings fixed the g-sync stutter problem for me:

Monitor Technology: Fixed Refresh
Preferred Refresh Rate: Application-controlled

