IF you bought your pup from a knowledgeable, caring and experienced breeder and you were impressed by the condition of their dogs, then I really can't understand why you would want to change from the food that they have recommended. But if you do decide to change the food, then please leave it for a little while - the pup is having to deal with a lot of changes and you'll do it no favours to change the food as well (unless it is being fed on complete rubbish!) Hills is fine, Royal Canin, James Wellbeloved, Arden Grange, Technical, Burns are all fine too. Some dogs do better on one than another.

And in answer to your second question about water - then a very definate YES - water should be available to dogs at all times, and is even more important if they are fed on a dry food and the weather is hot.