One thing to look for, in regards to "smarts" is the smarter pups tend to be the more highly ranked ones. When I got the two mutts I have now, there were eight out of 13 pups left, and the "boss" pup was busy running the others around, basically herding them, except for one, all around. That one just watched the boss run himself ragged, and walked up to us, climbed up on the couch and went to sleep in a minute. We said, "Well, there's one!". The other one we took was a female who seemed to stay with the other one all the time, in the pics the "breeder" had of them, she was always next to him, or behind him. From the pics and the way the other pups reacted to him, it was clear he was the "enforcer", the #2. Almost all the benefits of #1, without all the work, all he has to do is back up the boss if the other pups get too rowdy. It's a smart way to go.
He's scary smart, and is my "Dog of a lifetime". He's the healthiest dog I have ever had, too. We named him King, and he deserves it. The other one, Molly is a nervous nelly who rules the yard, again, doing all the work of killing invaders and harassing the poor dumb dog stupid enough to jump over the fence, with two exceptions, the female shepherd next door is allowed in, and a huge Lab pup who already weighs over 120 pounds and is skinny as hell, is also allowed to come in to play with King. Molly doesn't like it, but King decides what happens in all matters. Molly has tried to pull a "Coup", occasionally, and it's gone very badly every time she tries it. Sadly, she has bad hips and allergies.