It shouldn't matter as long as they are all the same and you aren't using an odd vane (like NAP's Quickspin). "Normal" vanes or fletchings can be done either way.
Most people will not notice any difference in a right or left “ standard 2* offset helix” ( straight jig clamp) it becomes more noticeable when you start offsetting the vane or feather with a heavy helical offset. I use an 11* helical offset in a LH jig for maximum stabilization of my arrows shot from my 52lb. Longbows and recurve.
For plastic vanes there is no left and right, for feathers there is definitely a left and right. For compound shooting, making them all the same is more important than left or right twist.
This is the style my father uses but straight fletchings. I can tell you hes horrible mechanically so if this works for him anyone can do it.
