That thread is out-of-date as BPM is supported as a read-only column which Opus will show. (I've put a note in the thread in case other people find it.) Opus still cannot edit BPM tags, though, so you're still right that an external tag editor will be needed to change them.
Abr's other answers are correct/up-to-date. Support for rating columns and more advanced tag support are both on the feature request list, FWIW.
Yes, see the FAQs for why we ask that people do this.