I personally think rotating is a good idea. Yes, it reduces the risk of developing food allergies due to over exposure, yes different manufacturers use differing supplements and feeding a variety can keep the digestive system stronger and not so sensitive to change.
As far as feeding a regular puppy food versus a large breed puppy food for larger breeds, there is typically a difference between puppy and large breed puppy food, primarily the calcium levels and caloric density of the foods. Feeding a nice all life stage food is OK, too, as long as the calcium levels in the food are appropriate for a growing large breed pup.
The calcium and mineral content is particularly important until the pup has reached sexual maturity and at least 80% of the expected adult height. We have to keep in mind that puppies are not able to regulate how much calcium their bodies absorb, adults can. The mechanism within them that regulates calcium absorption does not fully come about until at least sexual maturity, later for some dogs.
Too high of calcium in the diet has been linked with increased risk in bone and joint problems. As well, too little calcium can certainly cause terrible problems.
A large breed pup (large being any dog expected to be 50 lbs. or more) should have at least 2000 mg of calcium per 1000 Kcals consumed and no more than 4500 mg per 1000 Kcals consumed. Somewhere in the middle, I like to see around 3000 mg per 1000 Kcals consumed, is ideal.
Regulating a large breed puppy's caloric intake, as well as calcium consumed, helps to ensure a nice even growth to minimize the risk of future bone and joint problems.