There is no "right" answer to this. It all depends on what you're used to and what you can do better with. It can either be on fast so you can turn around faster, or more moderate so you can aim better. It's all up to you.
No it doesnt...I use sureshot...I get alot of headshots but thats because I aim for the head and burst....but pfft whoever told you that is lying out their ***.