The smallest container Doc recommends is 7 gallon but bigger is better. There are a few who do grow in smaller containers with good results like
@Graytail. It can be done but you can also expect to have some issues. The end product will still be excellent but you may have some plants that look like they ran out of gas.
If growing seeds it is recommended to give CAT drench all the way through flower since it is the most reproductive of the drenches. I'm almost certain Doc has run plants on straight Growth or Transplant all the way through flower and the results are different terpene profiles. Ideally you want to follow directions before experimenting and it is better to alternate the drenches. Flipping the soil charge from + to - keeps the plant in high gear.
I don't know if there is a bad strain to grow but some can be more challenging like the plants that were bred for hydro and have weaker root systems. Any of the landrace or IBL strains thrive in this system. Anything from ACE seeds loves high brix. The new frankenstrains do well too you just need to feed a little heavier and probably use the snake oil additive.