@Amanda
There is this common perception about grain-free diets floating around the internet that they are “superior” or “less allergenic” than diets that include grains, even grains like corn. This is completely false. True food allergies are rare in dogs firstly, but the more common food sensitivities yield a different immune response and food intolerance works completely differently than that. Grains are not a common source of allergen despite what many blogs will tell you.
Genetics is going to play a bigger role in the health of the dog. Purebred dogs coming from breeders who health test and cull bad traits out of their breeding program are the kind of breeders you want to associate with and buy from. These are the folks looking to better the breed they love and preserve that breed.
As far as wanting an easy answer to nutrition, it’s not easy. If going through a quality breeder they will be as much a part of your life as the dog is whether you want them to be or not. They will help you select a good food appropriate for the dog. Your vet can help as well.
Your puppy should be fed whatever food the breeder uses for the first 3 weeks it is home with you to avoid added stress which can cause GI upset. Doesn’t matter whether you “approve” of the food or not. After the pup has adjusted to the new surroundings you can begin to do a slow transition to the puppy food of your choice. It doesn’t really matter what brand you pick per se as long as it is formulated for a puppy (like I mentioned in my previous post).
