Most seeds being sold are polyhybrids. Hybrids are crosses of 2 separate genetic lines. For instance Thai + Malawi or Afghani + Columbian. Those would be hybrids. If you were to cross those two hybrids you get a polyhybrid. Most of the stuff out there has been crossed to eternity these days.
As for potency that's going to depend. Some make crosses to increase CBD levels and lower THC levels. Some make crosses for potency, some for CBD, some for the color purple, etc...