Whether deposits are refundable or not depends on the breeder.
Personally, I think you should narrow it down to a few and develop a relationship with the breeder over the phone, in person, however. Tell them when you are looking to purchase a pup (when I was looking for Soda I did not want a pup for a good 6 months). Keep in touch from time to time so they can let you know what might be coming. I truly think going about it this way is better than looking at websites for pups to be listed. I will have a relationship with this breeder for my dog's entire life. I want to be sure we mesh well or it could turn into a huge headache. I don't want a pretty pup from someone I can't stand to talk to.