Correct, Explorer has some metadata columns that Opus doesn't have, and vice versa.
If the data you are interested in is available to VBScript or JScript then a script add-in could be written to add a column to Opus that displays it. The Office apps tend to have good automation support, so it's possible that approach would be the way to go, although I don't have experience with automating Outlook.
Column: Word Count for Microsoft Word documents is a similar script add-in that provides a column showing metadata extracted through Word's automation support.