These rims look absolutely great. I guess they are 8x20"
What is the ET?
In theory it seems like 8.5x21" should work with 245/45R21 but the tyre choices are quite limited so tyres relatively expensive.
The question about the relative weights of the various rims, and for that matter other options like the panoramic roof, is something I would really like to see more about. It would be brilliant if some forum members were able to stick one of their wheels on a set of bathroom scales.
I once had a car with forged alloys, the reduction in unsprung mass made a huge difference to the handling.