here are some general comments

1. on carbons a offset fletch with 4" vanes or feathers works great
2. a helical on a carbon with 4" or 5" is harder to tune unless you have a fall away rest.
3. feathers privide more drag, more forgiving, and lighter than vanes but vanes are more durable in hunting situations & bad weather.
4. Both shoot great if you tune your bow to what you are using.
5. on Aluminums that are size 22XX or bigger a 5" helical is a good choices but 4" will also work.
6. in general the bigger the cutting diameter of a fixed blade broadhead the more fletch you should use with a helical if you get good rest clearance.
7. If you shoot fingers use a helical with 5" fletch for hunting. feathers or vanes both work good depending on your arrow rest.
8. for traditional archery feathers in at least a 5" helical is currently the most popular.
9. right or left dosn' t really matter as long as you don' t switch back & forth. generally a lot of shops will only stock right or left wing feathers depending on what they like with vanes they work either way, right or left helical.