[DigiTechSupt]

You cannot currently playback 16 bit files and 24 bit files in the same session.

You can dither the output of a 24bit session to 16 bits (or 20 for that matter) using one of several different plugins by Digidesign or one of Digi's Third party developers.

As far as the OMF situation, It is not currently possible to create an OMF file in Pro Tools. IF you need to get audio from Pro Tools to Media Composer, we recommend that you bounce each track down to one contiguous file in Pro Tools, import each into MC and spot them manually. It will be necessary to convert those files during the bounce process from 24 bit to 16 bit so that MC will be able to import them.

Thanks,
Jon Connolly