This should be posted in the Ideas forum, but I'll answer anyways:
1) Badlands is the most versatile; with structures, grasslands, dirt, water, and roads, this would probably be your best choise for an RPG.
2) I'd need to know what the RPG is about.
3) Player Colors: This really has no difference except for looks. I prefer an RPG where everyone is generally the same color. If you have a town with blue people, make the characters blue.
4) Interactivity: Use a system where you can talk to anybody. If it's like the average RPG (shops), make it so you don't list walk in with a mute shop-keeper and buy an item without even opening your mouth. Give the players a personality throughout the story.
Edit: Chu is fast! it was already moved.
