So I know this is an old article but I figured some people might still need help. I have a GeForce RTX 2070 and I had recently installed a clean OS on my PC and when I ran UE4 it was super laggy and terrible FPS drops. If I focused my cursor into the editor window the FPS would go back up to 120FPS but if I focused my cursor into the content browser, after about 5 seconds it would drop to 5 FPS. My CPU and Graphics card weren’t even above 10% while this was happening so I had no idea what the cause was. Until I realized I had installed the Game Driver for my Graphics card and not the Studio driver. I installed the Studio Driver and restarted my PC and now I have 120FPS across the board.