I can't speak specifically on your breed. But I will speak in general. The best thing to do is to make sure you are giving the dog some good food, Whether that is a good kibble or Raw diet. You feeding it a different ratio of protein than the breeder will not make it grow faster or slower. That will be determined by genetics. Understand that the majority of a dog's necessary nutrients come from either protein or fat. Protein is the builders. It build all the cells. It build skin, fur, muscle, etc. Fat is used to supply energy, shiny coat, etc. In regards to growing too quickly it is my understanding that this refers to additional supplements like calcium. People think in terms of humans or human nutrition. We need strong bones so we need more milk or calcium. So we know we have big dogs. We give them calcium supplements to help develop their bones and teeth. This can harm the dogs especially larger breed dogs that have a very different growth rate than other species. My suggestion is to avoid supplements for bone, joints, and teeth. Allow them to get nutrients from good sources of foods. If you use kibble check out https://www.dogfoodadvisor.com/ . They a non-biased in regards to different brands of kibble. If you choose to feed Raw make sure you do the research and get a good plan. It should be more than just giving them Raw leg quarters. It will need other nutrients. We all have our preferences. But you need to make those decisions for your dog. My way is not the best way. It is just my way or the way I think is best.

I learned on https://www.dogfoodadvisor.com/ that many of the top well known dog foods that I was taught was the best are worth feeding to a dog. I remember as a child these foods cost more than most foods. They had the big name. Vet recommended them and so did everyone else. Today there are more brands. Even some of them have bigger names, but not always a bigger branding. But you might be shock at 3 of the biggest well known brands and their ratings.

By the way I didn't attempt to put in the brand that you are using or the one that your breeder uses. But you should check them both out. If I am going to use kibble I would try to stay within the 4 or 5 star brands. Also, if possible grain free as dogs don't metabolize grains like humans. They are carnivores not omnivores. They are opportunist too. They'll eat what is in front of them. But their bodies don't digest everything or at least not well. They have a short digestive tract. Things that might give us salmonella will not affect them.

Good luck