I recently installed 1.14.4 and i instantly noticed how "laggy" the mouse felt.
It's especially noticeable on a 144hz monitor.

It seems like the game updates mouse input at a fixed rate now (60?).
But it almost seems like it's uncapped in window mode.
If you switch to fullscreen it's very noticeable.

There's no difference with Raw Input on or off.

Update: Upon further investigation; it seems like it's a VSync issue.
It seems like the mouse doesn't update with VSync (or something).
If VSync is off, the jittering and "capped felling" is gone.
Which was not the case in 1.14.3.