I just "BET" on the line I think will win.
I only have a 2 bet system. If you want to talk about units, it would be a 1 unit play for almost all my bets, and than a 5 unit bet on like maybe 1 or 2 a month (probably only around 3-5% of my picks).
Because how I look at it: If I think I see an edge, I'm going to put my bet down, and if I see a huge edge, like wtf are thinking edge, I put down the 5 unit one.
Think about it: People always talk about a 1-5 unit betting spread, or more, but if you are a full time bettor you probably only win 55-57% of the time (not counting the 60% and 50% years); so if you are only winning 2-4% over the vig, changing your betting, will show that, if you are going to make a bet just put down the same bet everytime, because if you think you are going to win, bet the amount your bankroll will allow you.
My view on bankroll: bet 1 or 2 %. and recalculate bankroll every 3,6, or 12 months.