Welcome LEX. The holster that came with your XDM is fine. In the future, you may want to upgrade to something with active retention. Gun grabs can be a problem for OC, although they are rare. Retention is not as important for CC. I think the first thing you will notice about OC is that nobody else notices or cares. When you first start to OC, you assume that you will stand out like a flashing sign. That is not the case. As far as the empty holster, if that makes you more comfortable, go ahead.