Misleading
The win rate for the 1-6 spread I quoted used the same unit as the 1-4 spread, so it would require a much larger bankroll for the same risk of ruin. Sorry to mislead you.
With a fixed bankroll, 1-6 wins only slightly more per hour than 1-4, but you can wong in at -6 rather than -2. You'll have to decide whether it's better to play more hands with a smaller unit and larger spread, or fewer hands with a larger unit and smaller spread. Whether or not you have to make awkward bets with multiple denominations may also be a factor.
I'll leave your other question for someone who knows more about unbalanced counts.