I think the chosen post must be selected on the bases of content and easy language. If a post is written in 3000 words and express a ten sentence content, I don't think it is worth of your reward and upvote. I have seen most of the selected articles too long to be reasonable for any educational purpose.
Yes I also do write with steemstem tag, hope one day my blog may be visited too.
Appreciate your efforts for helping the people with good content.
Voting % depends on a lot of things:
Long posts that "answer" to the above criteria surely qualify for an upvote more generous than an equally long post that has not much to say and repeats the same thing over and over again. The same goes for short posts that discuss more complex ideas, but don't elaborate on them.
Thanks for the engagement and positive attitude. Personally I didn't expected so elaborated reply.