Generally the veneers should go from end to end.
Is this a one piece bow, or one of those bolted together 3 piece designs? If it's one piece is this all wood, or wood under glass? Veneers can be spliced together in the handle/riser area. But you would not want all the veneers being splicced together in exactly the same place.
What width veneers? Again, what design are you building? Whose plan? Or are you making it up as you go along?