Well, I don't really have much to say about this (maybe others?) but:
- The Chrome Web Store is the Android app, packaged using something called ARC Welder specifically to run as an Android app on Chrome OS.
- If your Chrome can run Google Play, then you're getting same Android app, also repackaged to run as an Android app on Chrome OS, but this repackaging will now happen "transparently" somehow (in other words, "Google magic").
What problems with attachments are you having, specifically? Can you elaborate please, including what you do and what happens and error messages if any.