Just finished seven arrows for a short horse bow. I favor straight turkey feathers of at least 6" in length. These are 6 1/2" and 3/4" in height. I like a little helical placement. I've recently been using a Pope and Young cut as shown by the two arrows in the second image below. These are also attached with a subtle amount of helical orientation.
Because I shoot a non-center cut selfbow , favor a heavy point with most of my shots typically close, I like the idea of the fletching grabbing a lot of air quickly so as to straighten the arrow out as quickly as possible. For any significant distance, these arrows would, of course, provide too much drag and be a poor choice.
Recently investigated a number of Plains Indian arrows, primarily Sioux, Cheyenne, Kiowa, and Arapaho. The 20 or so arrows I examined (via print media), they typically ranged in length from. 5 1/2" to 7", with an average length of. 6 1/2". Most all were cropped short, typically about 3/8", and placed in straight alignment with the shaft.
Perhaps our old friend Saxton Pope said it best with his final few words on the subject: "Mr. Arthur Young cuts his feathers in a long parabola shape. [but] These things are largely a matter of taste".