Can I put camera look in FixedUpdate and if no, why

I’ve seen a lot of advice that said not to put any camera movement in FixedUpdate and use it only in Update and LateUpdate. Why shouldn’t I do that?

if you use Input.GetMouseButton or Input.GetTouch functions inside FixedUpdate, it may work wrong. Because Input.GetMouseButton and Input.GetTouch shows state from last frame. So inside FixedUpdate you can “miss” frame where mouse button was pressed or touch was touched.
You can divide your camera look script into two functions.
Place code, where you detect clicks or touches inside Update function.
And code to move camera, you can place inside FixedUpdate. You can set boolean variables in Update to control movement in FixedUpdate.

You can put it in FixedUpdate but you should definitely put the inputs Update.

As Kennai just said, putting input in FixedUpdate will often result in the input being wrong.

Reason two is that even though FixedUpdate is for physics updates, putting camera movement into FixedUpdate could result in choppy camera movement as the camera is updating movement slower than the framerate you are running at.