Well to answer your question, yes a dog can absolutely harm your babies, all of them, in an amazingly short amount of time. And yes, some dogs can learn to get along. A whole lot more dogs cannot ever be trusted. Or they get along for a while and then in a moment when the owner isn't there/isn't watching the deed gets done. Maybe dog gets bored or just gets over stimulated by running, squawking chickens, who knows, take your pick. Just take a little time to read previous posts in the predator section here. Lot's of sad stories involving dogs and chickens. You will have to decide if you are willing to put your birds at risk, they are the ones who risk suffering an attack.
In all my years of chicken keeping I've had two dogs who were perfect with my chickens and now I have one who is pretty good, but I do not leave this one alone with them, ever.
A puppy in particular is not to be trusted with chicks/chickens. You will need to spend a LOT of time trainging the dog and that training will need to continue for a very long time. Do not ever leave them alone together. After your new dog is fully mature and consistently shows no sign of interest then maybe you will turn out a dog who is good with the chickens.
It really will boil down to the individual personality of the dog you bring home. There are representatives in every breed of dog who are good or bad with chickens. Not trying to be a downer here about mixing dogs and chickens, just trying to be realistic. Personally mine don't ever mix.