Its a few years since we were puppy hunting - and things might have changed for the better, hopefully someone will advise you, but my experience was that although there were some good breeders on there were some poor ones as well. Some were not even sure if their puppies were show or working, and asked what I meant
I used Champ Dogs and looked to see who health tested their dogs, and then looked at websites to get an idea of if I liked the feel of things. I have to admit to not being very knowledgeable about what to look for and what to avoid back then (5 years ago) and might do things differently now.
good luck with your search