Editor Lag (4.12.5)

Same problem here: fast viewport, editor unusable at all .
hardware: Dell 7559 i7 16GB RAM, gtx 960M. I’ve the right settings in Nvidia control panel. I also disabled notifications in windows 10 pro. I’m not running any software mentioned in the conflict list here A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums.