Update. I ride/race the Red XPLR 13 speed drivetrain for gravel. I am trying out the new YBN flat top chain, my results so far: back pedaling the bike with the YBN, with a straight chain line, one can definitely feel that the YBN has less friction than the Red E1 chain. Out riding, the YBN chain seems a tiny bit noisier, and does not shift quite as perfectly as the Red chain. But, that is not to say that the YBN chain is a problem in any way, it never misses a shift, or is slow to shift, it is just not quite as “perfect” shifting as Red. Given that folks report shorter wear life with YBN chains, I am going to use the YBN for races, and continue using SRAM chains for the rest of my riding. All observations were with a Silca waxed chain.