Prototype. There is a reason why that word was invented. It used to be "we should have built a darn mockup thingy out of cheap materials we are such dorks now we wasted all this money on virtual baltic birch!
You and your baltic beach.

You don't want to experiment and learn, just talk.
There are no shortcuts.
Headfones have through the head left to right panning. Sometimes this is without the room (in ears, closed back) and sometimes with (open back) it.
Open back helps with the impression of spaciousness by letting you hear the room you are in. Stick your head into a closet full of hanging clothes and see what happens to their sound.
I am also not refering to hrtf or other things of that nature.