RE: Shooting with both eyes open?
In general it is better but there are a few that can't do it for whatever reason.
The main reason is you have a full field of view,which makes it much easier to stay on the right spot of an animal while aiming.
Another advantage is a relaxed face(no squinting).Alot of target shooters will use a cover over their eye,so they can keep it openfor this reasonif they have trouble aiming with both eyes open.