Gunther was on Iams for Hmmmmm........
at least the first year of his life. Was better than the purina and beneful the breeder had him on. And he did perfectly fine on it growthwise, healthwise and otherwise.

I think tho I had him on the adult I don't know if I ever had him on the puppy food. We did switch later to Nutro natural choice and are now on Taste of the Wild.
I understand you have to go with what you can afford and the high quality foods are not always manageable. I was going broke trying to feed Evo, although Keiko is still on that for the moment.
I use the furminator on Keiko on occasion. It works alright. But unless your pup is loosing undercoat it probably won't be doing much. When they are switching over from puppy to adult coat they do look kinda scruffy and poofy in places........
....but as that's not really undercoat I'm not sure the fuminator would take the hair off as well?