Yeah, there's sort of a bell curve to the ideal reddits where everything in the middle is totally serviceable. However, too small and the mods become overwhelmed and have to overban/overmod to keep up. Too large and the mods get powerhungry and ban in accordance with their own political values.
Yes, although I think the latter is carefully organised, probably by well-funded groups.
E.g. /r/worldnews have 36 million subscribers, and I think it has more influence than even big newspapers, and this is controlled by anonymous moderators, who for all we know can be a team working for the same organisation.