There is an issue that creates strong lag and fps drops with a mouse polling rate of 1000Hz.

For example, in the provided video (with configured 1000Hz):
While I don't move my mouse, I get around 100fps, but when I move it, it immediately drops to laggy 10 fps.

This bug also happens with 500Hz, but not very noticeable, but still. At 125Hz it will be completely unnoticeable.

My hardware is a Razer Basilisk Mouse, not sure if it happens with other mice.
I saw this as "resolved" in other issues but created a new one since it is still an issue.