Hello Kate. Welcome to the forum. Yes, it is confusing selecting a suitable food for a dog, particularly a puppy. There are so many on the market. There is a thread here
which might be helpful for you.When you have looked at the thread, please feel free to ask if you have any questions.
Products that are labelled 'puppy' contain higher protein levels. However, there are many high quality dry foods that already contain more protein so if you choose one of these there would be no need to change when the puppy gets older.
A good place to start is the Dog Food Directory
because if you use the filters it will narrow down your search. I always tick the boxes for clearly labelled and no red ingredients. If you use these in conjunction with the rating slider set at 75% to 100% it will return the better quality products.
These days we are fortunate in that we have different types of dry food. Most are extruded which means they are highly processed and subject to high temperatures in the manufacturing process. There are also baked foods which are processed slightly differently. Cold pressed products are very different as they are not subjected to high temperatures and they are becoming quite popular now. There is a thread about this type of product here.
They are often all age so you would not need to change food as puppy grows - it is usually the quantity that is adjusted. Added to this list there are a few foods that are freeze or air dried and just need water adding to reconstitute them. There is a better explanation about the types of food here.
Dogs can benefit by having some variety in their diet and the problem with dry food is that there usually isn't any. You can enhance dry food with a little fresh, cooked food if you wish. We have a thread about enhancing dry food here.
I have given you quite a lot of reading there but learning something about dog food will pay dividends in the long run, particularly when starting out with a puppy.
When you transition your puppy to a better quality food, take things steady and gradually increase the new one as you decrease the Royal Canin.