I have always used straight fletch with a slight offset. Even a straight fletch with no offset will spin an arrow just because of the shape of the feathers. I shoot mostly self bows and found, for me, helical fletchings are noisier than straight fletch and they make my arrows slower.
I would suggest trying straight, straight with a slight offset and helicals and see what works best for you, with target points and the broadhead you normally use. I'd bet you could find someone that would fletch an arrow, or a few arrows so you could try them before you bought a jig. Pat