If you acquire a puppy a from a Real Breeder, then it has been matched to you based on your lifestyle and request. However same as a child, the adult that your puppy develops into, depends on what you do going forward. So 50% is what you get, 50% is what you do, of course this is called Nature / Nurture. If you want your dog to be highly sociable to all people and all dogs, then you need to start lots of socializing AFTER 12 weeks of age. Keep in mind, that highly socialized dogs will have little to no protective instincts.
Most people socialize their puppies and dogs with their close friends and inner circle, but do NOT socialize with people beyond that to preserve some protective instincts. This is all up to you.
An Authentic GSD puppy is approximately 22-28% Wolf, which is a good thing. Wolves are incredible animals, and a Wolf pack is simply a Wolf Family- Husband and Wife, their children, and possibly another adult female or two to help out with hunting and protection. Your dog, unless highly socialized will be very pack oriented to your Family and your other dogs. So unless highly socialized to strange dogs, your dog will be aggressive toward strange dogs, and attempt to ward them away. This is instinctive Wolf like behavior to protect the Family and Territory ( your Land). So there are pros and cons to over-socializing.