That filter you're describing typically uses a media called calcite. It is an inexpensive media and is easy to periodically replace. If you don't have that piece of equipment yet, do yourself a favor and make sure you get one with a Vortech tank. Can it make the water same for contact with copper? Yes.

When it is time to change your RO membrane, consider a Nanofiltration element - they have lower rejection rates.

Russ