High fletch are never needed, unless you always want to see your arrow in flight. Nothing better for that.
That said....I always use the 5.5 highbacks because.....I can get away with all kinds of release errors, arrow spines, darn near everything and still get decent arrow flight.
Yes, I think they slow down the arrow, a bit, mostly farther along its flight than we care about in hunting situations. They probably make more noise in flight, but I haven't noted a -problem yet. They DO catch a stiff side wind. You can tell because the arrow turns sideways in flight !
They certainly allow more leeway with broadhead stabilization.
Man are they pretty though ! Try red and white....looks like a lazer beam in the air, right to the target or critter.
ChuckC