Hi, I finally had time to answer your thread. Sorry I ignored your PM for so long.
1) Can you please tell me the temperature of the CPU while gaming? CoreTemp can help with this. http://www.alcpu.com/CoreTemp/
2) When Nvidia updates your drivers, they don't uninstall the old ones before installing the new ones. This is usually fine, but once in awhile, the different drivers will begin arguing with each other and GPU performance will be in the toilet.
I would like you to fresh install your drivers. I will explain how below.
1) Download DDU, extract the contents of the .ZIP folder to your desktop but don't run it yet.
http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
2) Download GeForce Experience for help with seamless driver installation. Don't run it yet. https://www.nvidia.com/en-us/geforce/geforce-experience/
3) Restart into Safe Mode. To do this, open the Start menu, open the power menu and hold Shift while you click on Restart. You're greeted with a fullscreen menu. Troubleshoot, Advanced, Advanced Restart, Restart. It may be called Advanced Startup, I always forget. Either way, it's the only one that mentions restarting.
4) Once logged into Safe Mode, run DDU. Take a moment to familiarize yourself with the program, then use it to remove all Nvidia drivers.
5) If you've never had any AMD hardware in this computer, skip this step. If you've previously had AMD hardware in this machine, also remove all AMD drivers that may still be in your machine.
6) Restart normally.
7) Install GeForce Experience. It will ask you to create or connect an account. I created an Nvidia account via my email and I haven't gotten a single piece of junk mail from them.
8) Once logged into GeForce Experience, click on Drivers at the top left. From there, it will guide you through installing your drivers. Restart when you're done.
9) Take some time to play your games. Observe whether or not system behavior has improved.