Greetings dear friend.
I do not belong to that elite of powerful curators, as my voting power is only $0.0013, however I have seen how some friends such as @xpilar or @electrodo have created organized contests or topics to discuss where users are supported according to the contribution or content they have.
On the other hand, I would like to answer the questions according to my way of being to see if you are interested in implementing such a strategy:
Should I base my upvotes solely on the quality of the posts and thereby support people who already know how to produce?
If the quality is good, "YES", since everyone should have the right to be rated when it shows high quality content, I have seen users with a repute of almost 70 while their publications only contain 3 lines of text or less than 20 words.
Should I assign some of the upvotes to people to encourage them to become great authors?
Votes are the main motivation for us Steemit writers no matter what the value. But, without a doubt whoever receives a good vote will be able to increase their performance and power as long as acceptable content is presented for the benefit of the platform, if most of us send the support received a large chain of support could be formed.
How much should I direct towards diversification? For example, to make the place more interesting by upvoting authors from many countries (that may follow ethical rules that would be called unethical elsewhere)?
All those who are loyal to the rules deserve support, here in Venezuela we live in strong times and sometimes I find it difficult to publish a post either because there is no internet, computer or simply because there is no electrical service.
I will always be grateful to those who seek to support others in a disinterested way and with all good will, God bless.