Wow, this seems to fix the issue for me too. On 4.16 even an empty map was sometimes giving me under 10fps, I even completely wiped my graphics drivers to fix it a while ago but it came back and I never connected it to the nvidia overlay (now I’m thinking the driver wipe just worked because it ended up disabling the overlay). It almost seems like the main editor window isn’t receiving proper focus and is behaving like it’s in the background since whenever I see the low fps and check cpu/gpu usage both are super low (but disabling that in the options didn’t seem to help either)