Yes choosing optics would be nice Mounting closer or farther from the face has almost nothing to do with dot size in real life, it just the matter how much "closed" is your eyesight when you are looking through the scope and how fast is your transition.
And OrgazmO I have to partly disagree with you. If you have Picatinny on top you can choose where you like to mount you optic sights. But yes it's smarter to put on in front of receiver Are you in service or just for hobby dealing with weapons?