I think you're also underestimating genetics... some people can add bulk easily, others can try really hard and they will become more tone than bulky. Your DNA dictates how easily it is for you to gain muscle.
Put Corey Maggete in the weight-room and he can become an even bigger monster. Put Steve Nash in the weight-room and no matter how hard he tries (working out + dieting) he will never have Corey Maggete type muscles.
I think Ed Davis will have a strong core but he won't be a big body. He won't look like Dorsey or Patric Young (remember that guy lol). Davis seems average athletically. He has a soft touch which is good but he's not going to be a bully inside. Hopefully his IQ will help considering his dad was a pro. At the moment it's frustrating to see him and Amir swat at everything and pick up silly fouls.