Consistent FPS Drops based on Refresh Rate

[Resulon12]

What GPU do you have? I would refrain from using "Main Display Refresh Rate", instead use "None" and then, open your GPU settings app (Nvidia App) and locate the driver setting for "Maximum Framerate" and set it to just below 144, for example 142.

Doing so will prevent G-Sync causing issues when the FPS go over 144, etc.

Make sure to turn off V-Sync in the driver setting as well.

Use Borderless Window mode only when FPS is set to "None" and your GPU can handle 80+ minimum FPS, 60 or less usually creates stutter and other issues.
I would use Fullscreen mode if you want to cap FPS at 60 on a high refresh rate monitor (120Hz+), also disable V-Sync manually as above.

"None" option disables V-Sync in the game only, driver setting overrides the game setting, so make sure to check that too.

Edit: Actually now if i put the fps ingame to 60 there are drops now aswell down to 20fps.
Thank you for the reply!
I tried what you said. The fps is now set to no limit but limited to 142 by nvidia and V-Sync is off but the issue persists.

My graphics card is a Nvidia Geforce RTX 5070ti

Actually now if i put the fps limit ingame back to 60 i now get fps drops aswell down to sometimes 18fps.