Why all these options what difference does it make. I understand the fact that you can fly in either of these modes but why have an option whats the concept even if you don't want the cabin for example just don't go in right?

frame rates

Basically Joe, if you have a top machine, you should be able to fly the 2d+vc+cabin with ok fps.But if like most, you only have low or med machine, you will get more acceptable fps by loading the 2d only. Loading the full gammut on a low end setup, would be a bit like trying to run a marathon with a sack of coal on your back when you are not a very fit person.The less work you hand out to your machine, the better it will perform.

Thanks guys!!! Now I have a better understanding i'm slowly coming along!