Hey Card and Dungeon,
Unfortunately, since Windows 10 is such a new platform, compatibility testing is still in progress for UE4. We currently do not have many machines dedicated to this OS since it is so new and has known issues.
As for the EVGA Precision X, if the engine runs fine without it I would suggest using that route. You will not see a huge change in performance since you are using a pretty powerful GPU already. We do not provide support for EVGA Precision X as this is not our native software. If it is causing the editor to experience issues when enabled, then it more than likely is not with the editor, but with the OS and the application itself.
Thank you,