I am speaking from my experience with mals, so this may or may not apply to other breeds...
But, what I've noticed is that there are the cases where picking a puppy is a crapshoot...but overall, in mals, what you see is what you get.
What I mean by that is that when you pick a puppy, most of what you see will remain static.
However, there are exceptions to the rule. Take Kaiden for example. He had SOME drive as a puppy, but was also content to hang out on the couch...as he got older, he kinda got goofy. He didn't really want to do the bitework. EVERYONE told me to sell him....Greg told me to give him a chance. Well, around 8 or 9 months of age, Kaiden exploded. He wanted to bite...was still calm and goofy, but loved to bite, and because he was so big, he progressed in his bitework rather quickly. He is only a little over year old, and Greg has him comfortably on a shoulder sleeve, and having gunfire (38 full loads) over his head...I end up half deaf, but he couldn't care....
Take his litter mate (who was originally supposed to be mine). This puppy was always insane. Always at the front to get the rag, etc. Well, he was also rather nippy. We currently have him here for training, and he's a beast...so much drive that he doesn't know what to do with himself!!!
At 4 weeks of age, Nisha was a beast, and she stayed that way!!!
A lot also depends on how you raise the puppy. I have some general rules of puppyhood for working dogs: lots of crate time, no toys in the crate, play time is limited, no playing with older dogs that might hurt him/her, no corrections, and no obedience....
I've seen several dogs go to $hit because some of these things were introduced.
"Rumor has it, compulsion is evil."
Sacha CGC - Dumb Lab
Nisha CGC, PDC, PSA TC, PSA 1 - Crazy Malinois
Drusilla SLUT- Pet
Nemo - Dual-Purpose Narcotics
Cy TC, PSA 1, PSA 2, 2009 PSA Level 3 National Champion
Axo - Psycho Puppy
Rocky - RIP My Baby Boy