Morten's Theorem on it's own doesn't say that much, but a big lesson to take from it is that nut draws are more valuable when players are in the pot with irrelevant draws. You will win way more than half the time, you will make a freaking fortune. While compared to those other three Lowball is a tedious bore, compared to Draw, terrible players have a much better chance to win. In the Draw example, the tens are about a 5-1 favorite. In the Lowball one, the two card draw isn't even a 2-1 dog.
Bad players have no chance in Draw poker.
Nope, and that's why that 300BB number is mostly useless, and wrong. Bankroll is more a function of circumstance than variance.