I went to puppy shaping class and then to puppy foundations.
Puppy shaping is for pups as soon as they are vaccinated so they are very young, we used treats there, but when we got onto puppy foundations (pup was about 6 months then) we used toys and praise more than treats.

Still use treats for some things and just praise for others.

I think its all about finding the balance of what works for you and and your dog!