I believe you are correct, the one investigative officer is usually a military judge who forwards his results to the courts-martial convening officer. Although, I do not have any personal experience with the Article 32 process.
The one big advantage for the accused in an Art 32 is that they can get into the prosecutions stuff before the actual trial.....discover, data, witnesses, etc.
If there's not much of a case, then the Art 32 is duty bound to report that to higher.
If it goes forward to a court martial, that normally means the evidence is almost certainly going to be difficult for the accused.