The quietest helmet is the one that best fits your head.
With that said, Shoei fits me best, but a friend gifted me an Arai
and it's quiet enough for me. I would imagine the Shoei RF series
and the GTAir in particular would be my first choice.
I have friends with second-tier helmets (Icon/HJC) that like them very much.
Unfortunately, you just don't know what's going to be quiet until you get out on the
road for a good rip.
Some helmets are more quiet than others but all can produce decibels high enough to produce permanent hearing damage at speeds as low as 40mph.
Helmet noise also depends on your riding position. Given this bike is more upright I've notice my rps 10 is not has quiet as it was on my SV650. I had a Shoei Qwest before the the rps. It was one size too small but quiet given the venting and aeros are meant more for upright riding vs the rf line.
Shoei Qwest works the best for me unless I'm riding hard and fast (in which case I'm leaning in more) - then it was my Shoei RF1100. I say was because it rolled off the workbench onto the cement - so I donated it to the neighborhood kid to wear on his little motorcycle instead of his bicycle helmet...