thinkingblade
Generally, the length of the fletching is tied to two things - first is the weight of the arrow/tip and second whether you are running broadheads or not. Light arrows, with light field or target tips need very little fletching or vanes to steer or spin them in the air, heavy field tips can need more simply if they overbalance the arrow so it tries to rotate around the short axis of the arrow. However, generally even short fletchings if helically attached so they spin the arrow can stabilize heavier points. The problem comes with ... Broadheads. Essentially, a broadhead is a canard on the front of your arrow which is trying to steer the arrow in flight. So the purpose of the fletchings are to spin the arrow creating a sort of boundary effect in the air from the broadheads to prevent them from steering. However, they resist this, thus the larger fletchings to force the arrow to spin and stabilize. There are really large fletchings for arrows called "flu - flu" which essentially act as a sort of parachute to prevent the arrow from going to far for bird or small game hunting, but that's relatively special purpose. Thinkingblade

DJ
Yes, fletching feather length effects the tail steerage of your arrows. The longer the feather, the more drastic the tail drag, and the more steerage it provides to the arrow. The shorter fletched arrows will likely fly faster, and won't drop as quickly as the longer fletching, but at the same time, they won't be as stable in flight. If you switch over from one to the other, you probably won't see any difference, but if you're mixing the two, you potentially could see different flight patterns for the different sets.