How to act as an editor?
From conversations with a mentor who was the editor-in-chief for a major journal, if you take the responsibility seriously, you need to have enough of an understanding of the papers assigned to you to figure out which referees will be suitable for a paper, while not taking so much time to read it that you can't process all of them for lack of time. As mentioned above, you need to at least a "high-level" read of the paper before assigning it to the referees. If the paper comes back with mixed reviews, it probably requires a careful re-read; if the reviews are uniform in recommending for or against publication, then it may not be as critical.

However, the editor will want to read papers when revisions come in, so that may mean going through a paper several times during the course of the review process.