which one would be best to get?

 

depends, pro-S only has height adjustability, where pro-C has damper and height. also, will you be DDing more or autoxing, tracking, etc?

 

Depends on what you are planning on doing with the car. Your goals, are you planning on slamming the car, or having a reasonable drop? What's your current knowledge of a coilover set up? How much do you have to spend on your suspension? Keep in mind you will need a rear camber kit.