Woolf,
The completed system is optional, but the bigger gens and most of the heavy electrical distribution are part of the basic empty weight, the mats are embedded in the normal blade airfoil and so cause no performance loss. The weight gain to have the controller, slip ring and the like installed is not too great, less than 200 lbs, I believe.
I believe the aircraft suffers some performance loss in icing flight, since the ice is allowed to accrete somewhat before being tossed off, but that usually just drops the Cat A ceiling a bit, and the 92 has a fairly good one. I will try and hunt some specifics and post them (now that I am on the outside, no promises!)