Whom to suggest as an editor when submitting a paper?
You are correct, selecting an editor the authors have not met avoids perceived conflict of interest, which is a good thing.  I think "editors were well known by my co-authors (no shared projects)" is also a good choice.

It's not always possible to eliminate all potential conflicts of interest.  I would prioritize avoiding selecting an editor whom I had coauthored a paper with, since that is a very important form of professional relationship.  Ultimately, assigning the manuscript to an appropriate editor should be the journal editor-in-chief's responsibility, not the author's.