60fps with vsync on is 16.7ms
60fps with vsync off is 16.7ms unless your monitor cannot sync to a multiple of 60hz.
So even tho they both 16.7ms between each frame one is more laggy than the other? deffo placebo.
150fps is 6.7ms, so you can pick up noticeable 10ms of frame processing time? to put in context that is 1 100th of a second.
Its adapting.
If I play for hours at 30fps, then switch the game to 60, things will feel weird sort of like they fast forward and too smooth. But then after say 5 minutes I Adapt and feels normal, then if I switch to 30 it will feel weird, and sort of jerky. But again after 5 minutes I adapt and is fine.
I have also tried from 60 to 120, I feel if I look really hard and sort of analyse it with a lot of effort 120 maybe feels ever so slightly smoother, but I definitely do not immediately pick up on it like swapping between 30 and 60. The bit I really struggle to understand how players of twitch shooters are saying their response times are better at super high framerates, I struggle to understand how a human body has that kind of responsiveness.