Highly dependent on journal / field. In mine (mathematics) most associate editors work for free, same as reviwers. The reviewer do all the things you say, and

Highly dependent on journal / field. In mine (mathematics) most associate editors work for free, same as reviwers. The reviewer do all the things you say, and in addition try to ensure readability & novelty. Most journals do have professional copy editing, but that's separate from the content review. I don't know how refereed conference proceedings work (we don't really use these). The only journals I know of that have professional editors (i.e., editors who are not active researchers themselves) are Nature and affiiliated journals, but someone more knowledgeble should correct me here.