Genetics will always be unknown from bagseed (until you smoke it).
But that doesnt change the fact that in those big mexican fields, there are TONS of very potent females. But since its grown in such quantity, they dont bother removing males and hermies. They use the males and hermies to basically just add weight for extra pofits.
There is no difference between the seeds in shwag and the seeds you get from seed banks. (where do you think they get their seeds?! lol) They know the strains, but the seeds you buy from banks are guess what?! Taken from "shwag" plants.
Regardless of where you get seeds, the end results are always the same. The only difference is you don't know the name, and the cost.
When you buy from a seed bank, all your buying is a name. In the end, street or bank, once grown they all do the same thing, get you stoned. The question is, how much are you willing to spend?