The thought of having to punish a puppy makes no more sense than the idea of punishing an infant child. Have you heard of anybody spanking a baby? The single thing that would do is make the baby cry, and make the adult feel bad. A small baby won't learn from punishment, and puppies are no different. Just like everything you do with a little baby is intended to let it feel loved, protected and close to you, the way your treat a new puppy could affect the way that dog perspectives you for entire relationship.
The one thing you will achieve by punishing a puppy is to make it scared of you. If you smack a puppy, even lightly, all it knows is the discomfort of the strike and the fear it feels at that moment toward you. It doesn't learn that it was doing something wrong because it's too inexperienced to grasp that concept.
If your little puppy is gnawing on something for instance, and you punish it with even a light tap, of course it will likely stop what it's doing. It's probably frightened of you know because it probably felt agony from the smack. It can't tell that it was being punished for what he was doing, however, so he does not learn the effects of his actions.
You will also damage your relationship if you roar at your puppy. A puppy will certainly stop what it's doing when you startle it with a scream. But again, the puppy doesn't understand the link between its actions and your roaring. Even the angry tone of your voice can cause your little dog to be scared for a second.
If you use these punishments on a puppy, the little puppy will learn to be scared of you, or at the very least it will learn that you can be mean. It does not see why you scare it, so it will not trust you. You could never have a good relationship as the dog grows as it will never warm to you.
Some dogs are extremely passive, and will respond to you in a very defeated way. Your dog might stay in line all of the time, solely out of fear, but it will not ever trust you. Other dogs have a more dour streak, and because they feel threatened by you may try to dislodge you as the one in control. If your dog thinks that it should be the leader of the pack, you have got a massive behavioral problem in your hands.
At the least, you won't have as good a relationship with your dog as you could have.
Use mild correction when your puppy does something he shouldn't do, just like a little child. Use delicate movements when you discipline your puppy and a kind but firm tone of voice, so that your dog understands to stop without becoming frightened.