If you suck balls at 6max you probably suck balls from the last 6 seats on a full ring table, in particular, you probably suck balls from playing in the blinds - so I'd work on getting a better understanding of late position play (button vs blinds, blinds vs button, blind vs blind) and then you'll crush full ring or 6max or whatever. The most potential win rate addition is going to come from these spots. Potential win rates are pretty capped when you are opening UTG into a bunch of people. If your opponents have massive leaks from the blinds then your potential button win rate will skyrocket if you abuse their leaks correctly.