RE: XPS 8700 - Games stuttering after upgrade
Ok, just guessing at this point.
do you see anything in windoze event logs when the stuttering happens?
Are you using WiFi ( hopefully not for performance reasons).
If you are not using Wifi, so consider disabling the hardware device. I've had some issues with Win10 and the WiFi-BT cards on other Win10 systems.
can you try some stress tests using Cinebench ?
www DOT maxon.net/en/products/cinebench/
If you can reproduce the stuttering with a benchmarking tool it should be easier to isolate the problem than with a game which as many more moving parts.
You can run rending tests on either the CPU or the GPU.
I can compare your results to my non-Dell 4790K / GTX 970.
my 8700s are not at my location so I can't test those right now.