I think you are onto something here. When you try and rush into having tons of followers, you can end up with a lot of people from category #1 or #2, where they dont log in or just follow too many people.
Also some follow-for-follow accounts don't actually upvote many other people, they mostly upvote themselves.
Getting quality followers is all about posting quality content and good comments. Based on this post I think you are in the right direction.