hopefully this will address your questions, but i'm not sure if it covers everything:
you do have to be a member of the WPBTCA in order to compete in WPBTCA championship events in november. membership is $35 for the year.
if you are a USA member you can get a scorebook through USA (http://www.germanshepherdog.com
). not sure what the rules are on being a club member in order to get a scorebook through them, as i'm not a USA member . . . if you're looking to get a scorebook on your pit bull, your dog will be listed as a mixed breed with USA. which is why i wanted to be with a DVG club, which does identify my dog as an APBT with his UKC LP.
you can compete in USA trials or DVG trials and i'm almost positive that both clubs recognize the accomplishments of the other. so if you are a DVG member, you can compete in a USA club trial and vice versa. but there is some kind of process you have to go through to get your accomplishments recognized. i think you might have to actually mail your scorebook to them to have it certified, though.
not sure what you mean when the WPBTCA says membership or club member . . . the WPBTCA is a club recognized by AWDF so membership refers to being a member of the WPBTCA.