The more helical you put on your fletching, the more stable your arrow will fly. On the other hand, you can put enough helical on fletching that they will slow down your arrows and create more noise than necessary. How much is necessary? Depends on many things.

Fletching size is one thing to look at. The more fletching you use - like doing a 4 fletch with 5" feathers - the less helical you need. The less fletching you use - like a 3 fletch with 3" feathers - the more helical you'd need to do the same job.

Fletching material is another part of it. A 3" feather will provide the same amount of stability as a 4" vane, so a same-size feather will need less helical to stabilize an arrow than the vane would.

IMO, arrow diameter, weight and speed is a big part in determining how much helical to use. A light, skinny carbon arrow is easier to spin than a fat aluminum (say a 2315 for example), so it needs less fletch and less helical than you'd need on the 2315. Since it's going to fly much faster than the heavier 2315 - and since air resistance increases by the cube of velocity for subsonic projectiles (speed X speed x speed) - you don't need as much fletch or as much helical to do the same job of stabilizing the skinny carbon as you'd need on the 2315. Or on a skinny carbon going 300 fps vs one loping along at a mere 200 fps.

That's what makes these goofy Turbo nocks work.