Detailed Issue:  Playing Skyrim SE vanilla the game starts out fine, GPU load is at 98-99%, GPU temp running 69c, GPU clock stable at 1405Mhz, memory clock stable at 3505.  I have the steam overlay active and the game is running at 59fps, my monitor is at 60hz.  This is all game related no adjustments on my part.  After 25 minutes the GPU load becomes erratic, my fps will be all over the place dropping down to 15fps.  All other indications stay stable.  Leaving the game and reentering does not fix it, if I enter League of legends my fps in the game is very erratic also.  The only way to fix this is to restart the computer. Other indications - CPU temp stays around 37c and it does not look like I am maxing it at all.
 
System Specs:  Case - Fractal R4          Motherboard - Asus Z170 Pro Gaming bios ver. 3016 date 12/27/2016      Processor - Intel I7-6700K Skylake    RAM - 16GB Corsair Vengence DDR4 3000 (2x8)   Hard drive - C: Samsung 1TB SSD   Second drive 1TP WD 7200rpm
Power supply - Corsair AX760 80 plus Platinum   CPU Cooling - Corsair H100i V2 water Cooler      Case Cooling - 2 supply  1 exhaust   Graphics - EVGA GeForce GTX 960 04G-P4-3969-KR 4GB (driver Ver 376.33)  Monitor - Asus MG278Q 27" 144 Hz Free-sync  (YES - I know the GPU is G-sync and the monitor is Free-sync so the 2 techs do not work together, my bad, did not know about this at time of purchase - I am hoping this is not the issue - would have bought the PG278 or PG279 monitor had I known)   Keyboard - Corsair K70 RGB Rapid Fire Cherry MX Speed      Mouse  - Razor Taipan
 
What Have I done: (Playing on full screen) I have tried reducing the game settings, I have reinstalled the game AFTER all updates, When doing the updates did them as clean install.   After searching the Web made following adjustments:  Changed Vsyncinterval in SkyrimPref.ini =0.  Using NvidiaProfileInspector made recommended changes to various settings that other have suggested - YES one at a time and many together in various combinations.  I have been troubleshooting this for 2 weeks know.  I changed cooling profiles to increase cooling on system and GPU, I was able to get GPU temp to stay stable at 48c during the entire period when the issue occurred again.
 
The only thing I see is the GPU clock maxes out at 1417Mhz and will only drop if I enter a building or dungeon and then pops back up again when I go out doors, but this will be there for 15 minutes prior to the issue occurring and even with reduced settings.  The Fps still stays erratic inside the building or dungeon.  And why is the only fix restarting the computer?  I can immediately reenter the game and everything is fine for another 25 minutes.  
 
I did hook up a second monitor - LG E2041 to the DVI port so I could place all the monitoring programs there while I played and could watch what was happening.  Trying to figure out how to get screen shot of this monitor so I can show what I am seeing. 
 

Are you using DP or mini DP?
Can you try using the DVI only and see if the issue still happens?

Issue IMPROVEMENT:  OK  so I was able to borrow an Asus VB248 144 hz monitor, it had a logo stating Nvidia 3d vision ready.  It did not have the G-sync adapter on it - monitor was still in the box.  Hooked it up using the same Display port cable and a HUGE improvement overall on performance and play.  The GPU was cruising at 1050 Mhz with Ultra settings, display was at 60 hz with a solid 60 fps.
 
So question is?  Is there an issue with my Asus MG278? or is it the Free-sync - G-sync incompatibility causing the GPU to overwork itself?  
 
Still plan on upgrading but may try to figure this out before pursuing the hardware changes.  Any thoughts?

Only ran it for 15 minutes, had to go to work, plan on more testing this evening.  But there was a huge difference in all sensor readings even in that short time, so I am hopeful.    GPU load was 75%, clock speed was 1050 Mhz, GPU temp crept up highest was 60c before I shut down, fps was a stable 60.   Before, the GPU load would immediately go to 99%, clock would go to 1405 mHz and then max out at 1418 mHZ, GPU temp would ramp to 69c in a few minutes and the fps would be 59hz and then drop to 38 hz even though game looked stable.  I am learning more about the adaptive sync and it appears the monitor is working too hard at this and over taxing the GPU.  I may try running the 278 on HDMI or DVI-D and see what happens.  Also, looking into changing display port setting from 1.2 to 1.1 but want to see if I can and what the difference is.   I really want to figure out what the issue is even though the 248 works  I want to understand what and why the 278 was having issues.