It's hard to explain this issue in text but basically I believe we should get the option to disable the "smart camera" in legacy control type. I have no need for the camera panning on it's own and I feel like it causes unnecessary FPS drops.
Here is a video explaining the problem and showing how it should be instead (or an option to have either):
https://www.youtube.com/watch?v=2n-8KEWViN8