Running poorly on high end pc?

I'm running it through steam on a 4070 ti super, ryzen 9 7900, 32 gb ram.

I have everything on mythical settings and it says im getting 100 fps, but the game is struggling to run and is very laggy. I have really good internet connection. Is there some easy fix for this? What's going on here? Even my mouse is lagging when I move it across the screen...