Don't think you will be able to use sub-divs seeing as how I doubt they are used in games. Polys only. No nurbs either. Also, I don't think you can un-triangulate. Triangulating is ment to be done when you are completely finished with your model. Usually, I model a little, triangulate to see how close my poly count comes to my cap, undo, then model some more, then triangulate again later, see how close I am to my poly limit, etc, etc until I realize that I shouldn't model any more because my poly count will go overboard. Then I triangulate permanentely.

Correct me if I'm wrong on any of that.