The M140i like any other F20 with 18 inch rims have low profile tyres 40(F) & 35(R) - the increase in comfort with changing over to non-RFT will be felt, you will feel a difference HOWEVER make no mistake...the non_RFTs might give-in much easier due to softer sidewalls. I had this experience with my Merc and then the 320d and M135i and my 320I…all had same tyre sizes….the Merc didn’t have RFT while the other 3 had/have.
The Merc I changed many tyred due to the getting cut and giving in easily to the bad road conditions we have while all the BMWs with the RFTs were much more resilient.