A shorter piece on OP 1 and 2.
1. The car actually performs better with non-rft. It just shows more of is inadequacies. When they say the suspension is designed for RFT, they actually means they design them to ride better with rft. Non-rft with current suspension performs better and ride better. You feel more body roll because you have better grip.
2. As non-rft is also part of the specs as BMW can't force the consumers to use RFT, the insurance should not be a problem. I have checked with my dealer and they say warranty is not a problem as well. But if you want to be sure, you better check with your insurance company.