This is true of literally everything. Are toys or food more reinforcing? Is social interaction a reinforcer? Is exploring a reinforcer? Is interaction with a novel object a reinforcer? You cannot answer any of these questions except with reference to how the puppies react. And the answer will often depend on environmental factors and change from day to day and hour to hour. Having a breed mentor is a good way to start, because it will give you clues about what might be successful. But in the end you have to rely on observation to know if in fact you’ve got it right for this particular puppy/litter.
Read more about the thermoneutral zone: https://www.extension.purdue.edu/extmedia/va/va-16-w.pdf