Wheel weight is performance... one advantage of a goblin body vs the Cobalt body is the fact that the weight gets cut, allowing the engine & brakes to easily throw the car around. Rotating mass (wheels, tires, brake rotors, etc) are generally considered to be 4 times more beneficial for weight reduction, meaning 1 pound saved off the tires is about the same performance as 4 pounds saved off the rest of the car.
Shorter sidewall is lower tire roll, but tire roll hasn't been much of an issue for me. Mostly trying to get soft enough rubber to connect the goblin to the road. Even with the stock motor, I recommend <=100 tread wear tires. Love the Toyo R888R, the Nitto NT05R, and would consider the Nankang AR-1. Will pass on 200TW tires, as the back end of the goblin swings around too quickly when pushed, and I want to catch the drifts, and keep the goblin on the road. If you never push your car and never get into a drift, then maybe 200TW would work for you... just not me, and my mad Max goblin.