Unless someone knowledgeable here can help you I recommend that you visit your local BMW Dealership and discuss the above with them. BMW wheels can be tricky and what you purchase may not fit your car.
I have 2 wheel sets (one for summer and one for winter). My winter set is 18x8 with Michelin ICE 225/40/18 NONE RFT tires on all 4 corners. I can tell you that NONE RFT are a difference like day and night and I highly recommend them. My summer tires will be NONE RFT and my RFT will be recycled