The slope on all the American standard channels is the same, I believe 1:6.
Radiuses vary by manufacturer, I understand. AISC books tabulate properties based on the minimum radius, and show clearance dimensions based on the maximum radius, if I remember correctly.
I suppose if you're energetic enough, you could work backwards through the properties and derive the radius from the tabulated I and S.
I don't recall ever seeing if the "average thickness" that is tabulated is the average up to the web, or the average going all the way to the back of the channel.
This information should all be spelled out plainly in ASTM A36 or ASTM A6, but unfortunately, it isn't.