The idea is that your display settings / pov are setup so that everything is visually correctly scaled from where you are seated. The screens could be 20cm or 3m away, visually you would want everything the same size relative to your position. And the closer you can put the screens, the smaller they can be. (It's late, make that paragraph sound coherent in your own head :D)
Edit: basically you need to match your real life pov with the ingame pov settings.
The halo will have the same effect as in real life. Because it's physically there, and we have two eyes that enable our depth perception, we can kinda look "beyond" it.