There is a fixed exchange rate between freeplays and cash bonuses for a given book. If they let you bet FP on anything, then $1 FP = $0.75 cash. At BOL/SB, they recently tightened up so $1FP is worth about $0.55. If you prefer $0.25 in cash over $1 in FP then you're a fool and being dogmatic instead of caring about profit. It's like complaining a $100 Amazon gift card isn't as good as $100 in cash and then taking $20 cash instead of the $100 Amazon card.
Many places treat a push as a loss so only bet FP on things that can't push.
You obviously want to bet them on the biggest dogs you can find.
MLB counts towards only half the roll at a lot of places.
If you ever get stuck meeting roll with low limits at a book like BetUS, note they count pushes towards rollover so soccer lines are good.