Hi, sorry for the late reply -- you can only change the percentage after you've obtained 500 STEEM Power. Before that, every upvote is a "100% upvote". After that, you get a slider so you can select the percentage.

I'd prefer if there was also a text box, as hitting the exact percentage is sometimes difficult. I'd also prefer if it showed you the dollar amount your upvote would be worth if you clicked it at that moment (one's upvote changes over time, but it should be very close to what happens when you click the upvote, because it should be using the same algorithm).

Additionally, if you use the eSteem phone app, it will allow you to change your upvote percentage, even before you've obtained 500 SP. However, when I tried to use it, I got an error -- I think because it was doing fractional percentages, which this desktop version doesn't allow (it goes from 1% to 100% in increments of 1%).

Oh -- and, you are correct, it is also based on your power meter. So, a 100% upvote when you have 100% voting power is the maximum you can reward someone.

Very cool that you're delegating! I agree, work together. One thing I could do more of is to try to "convert the enemy" rather than just downvoting and complaining. That Bernie jerk could be a future ally, like @sift666 now is.