The extra nock receivers were originally designed for those arrows with a rear taper and a glue on nock. If you are shooting any modern arrow with a removeable nock, don't worry about where the fletching goes, just twist the nock after you are done to properly align it.

As for the extra clamp, I have a bitz with both a straight and right helical clamp. I would have to say that about 80% of the time I use the helical clamp, but it is nice to have the straight clamp once and awhile.