Well, as I understand it for the 20 votes, you get the first 20 all at full impact (5% of total SP), then the 21st starts to reduce the impact of all your votes (each vote is worth ((1/totalVotesCast)*100) % so they decrease in effectiveness each time you upvote. I'm pretty sure this goes for posts AND comments.

That said, limiting myself to 20 is only so that me and mine get the most impact from my votes. If I didn't worry about it so much it wouldn't really be a problem to just vote away.

At some point (based on Steem Power iirc) you get the option to upvote at a set % so you can give full power to those you really want to help out and a lesser amount to those you want to support but aren't part of your strategy.

I think... lol