Well, welcome to the board! The sunroof i think is 60 lbs extra on the very top of the car. Not great for weight OR for center of gravity.
The
MCS 17" with runflats are 50 Lbs each, which is more than the 16", but i dont know how much. Those are very heavy wheels too. I'd recommend the cheaper of the two then buy aftermarket wheels and tires, as that's bound to be much, much lighter.
As far as i know the MINI Cooper RS is still just rumors. I've heard that MINI is under contract to use that same engine for the next few years, so it's doubtful the RS comes out any time soon, IMO.
Hope that helps!