I have heard that weed from the 70s era only had ~2% THC where now at least dispensary grade can hit 20% to 25% THC. That could well be due to the drug war selecting for more powerful highs in smaller packages, but i would think that would also reduce the quantity needed to get the high you want.
Delta 8 is legal here, delta 9 is not.
No idea what those are.
Delta 9 is regular old weed where delta 8 is derived from hemp. Delta 9 is quite a bit stronger than Delta 8 is.