Game feels laggy despite enough FPS?

I currently have the problem that my laptop RTX 2070 and i7-9750H feels laggy despite good FPS.

Here is a small example: When I play OSU and show this streaming, via screen transfer to Discord or watch a video on the side, it feels very laggy even though I have 144Hz and can play the game with more than 1000 FPS.

Now I'm wondering how this happens and how I can fix it

Cap the fps

Try VSync

Do you have a ssd?

Unfortunately does not help

Unfortunately does not help: /

C: m.2 ssd D: normal SSD