yes fletchings definitly effect arrow flight. 1st the size of your vanes you use can depend on the grain of your tips/heads, and Foward of Center(FOC) of your arrow. Far as offset or helical I like to look at it this way. The more spin you can get on your arrow in flight the better the accuracy in flight, much like a spinning bullet out of a rifle. Straight vanes have their place, mainly for fletching clearance problems. But I try to go with as much offset as I can get on my vanes w/o rest contact. The new drop away rests resolve that problem too. I hope this gives you the right idea.