That depends on the diameter of the shaft. You'll be able to get a greater angle of offset on a fatter shaft with a straight clamp that you would on a skinnier shaft.

For the most part if you're using a shoot thru, prong style type rest then the straight clamp will give you all the offset you can take before getting fletching contact. Obviously the helical clamp is capable of giving you a greater offest than the straight since it curves or bends a little further around the shaft. But you could also set up the helical clamp at a lesser angle and should still be able to shoot those thru the prong style type rest without contact.

As far as specific angles I have no idea. I just set mine up using the trial & error method until I find something I like & then I mark the settings on the jig. I use a straight clamp & it has worked well for me on anything from skinny carbons to fat aluminum shafts.