Well, the short story is:

Since HF21, everyone has 2.5 free downvotes and hordes of people are flagging various content on the trending pages. However, it's not all content, it's basically low quality posts that have bought a ton of votes. So you will most likely not be able to see any form of ROI on this one.

For starters, I would recommend that you read these posts:

• https://steemit.com/hf21/@steemitblog/hardfork-21-survival-guide
• https://steemit.com/busy/@anomadsoul/ocdb-and-downvotes-or-a-newsteem-approach
• https://steemit.com/abuse/@tarazkp/downvoting-is-sweetsss

There are a bunch of other articles you can read as well, but these three, including the comment sections of each article should definitely give you answers to any of your questions.