RE: 2-blade question....Does it matter
If you want the broadheads lined up on carbon arrows, through the broadheads on the bare shafts and line the nocks up to the broadhead then fletch them. I always put mine flat, for two reasons. One its less likely to cut my finger if the blades are out instead of up and down. Second arrows bend in and out upon my release and right at the bow the broadhead is not slowing this motion down.