You really can't tell how a puppy is going to be in terms of energy and sociability in a couple of short meetings (our current dog was super sleepy and cuddly the first time, and playful/energetic the second), but I do like to do the usual tests. Does the dog let you hold it without growling or trying to escape, that sort of thing.

My hunch isn't so much that the breeders are looking to match you perfectly but that it's a hassle having a bunch of different people all coming out, being demanding or wishy-washy, or whatnot. It's just easier for them if they make a quick decision.