The way I understand it, voting power doesn't really mean very much for us minnows. The higher your voting power is, the more weight each vote worth. The weight behind each minnow vote is so low that I don't think there much of a difference if you are voting at 100% or 70%.
Based on Dan's post from earlier this week, I think curation rewards are a function of your current steampower, voting power and when you actually vote (or your vote number). Since the steam power for minnows is so low, we usually don't get any curation rewards, at least I've never received any. Once you are a dolphin or a whale, you need to watch more closely how you vote. If you vote too often on unpopular stuff it will give a lower payout then voting on popular stuff less frequently.