so , with a 700x28 tire and a 40x11 gear , at 80 rpm, one is at 23-24 mph (37-37 kph), at 90 rpm = 26+ mph (42-43 kph) and at 100 rpm = 29+ mph (47 kph).
I think it's ok to coast at 30+ on an average group ride - different if it's clearly a hammerfest.
one could always get a 42 ring to get that lil bit more...
again, with 1x, the real issue comes up when you're at 20 thru 25ish and you're hunting for a 'happy' gear to maintain whatever pace the group is at. It's not a SRAM or Shimano or Campy thing, it's a 1x - 2x thing.
Ride On
Yuri