I used the 19 because thats what the AC are and I know they will fit in the frame with 25 mm tires. Not sure if can go any wider. The pinch point on the frame is behind the bb side clearance. I also thought that narrower rim with wider tire wasn’t good.
I’d like a 38 but have seen some in only 32 or so. Given my weight don’t want a much taller due to wind.
Also wondering about the FLO 45 Carbon Clincher a little more rim but has both carbon & al braking surface.