I have only used wads in my New Englander 12 ga. so I can't say about PRB's. I have used wads/wafers in my BPCR .38-55 and .45-70 and also .45-55 (TD carbine).

The shotgun is understandable on using wads, but not sure why it helps anymore for the BPCR rounds. That was the recipe that I followed. I must admit that the BP cartridges are a hoot to shoot. Playing with the accuracy is interesting. Never did try using rounds with no wads/wafers.