I can only speak for my breed, but an 18 week old puppy in Rottweilers is very much a baby. Puppies this age are usually glad to see anyone and everyone, dogs and people alike.
I generally start to see adult type behavior in Rottweilers as far as territory, guarding, dog aggression, and sexual behavior anywhere from 10 months to as late as 18 to 24 months.
Can't speak for the bullies, but this is how it is in Rotties.
You WILL see some adult facets of temperament and behavior such as retrieveing behavior, activity levels, general sociability, and drives at this age.