I don't know what you're intending to use Dragonfly for, but I can tell you I been a happy user for three years now. Been active only lately here... Well, to answer your questions:
-1- No. Those would have to be ported. What I know is that quite a few nuke modules have been ported already, those can be either found on this site, either on other Dragonfly sites. Please have a look in the block titled X-links to the bottom left.
-2- Yes. You can install multiple themes on a Dragonfly site. You can even allow each site visitor can select the theme he or she pleases most. From what I know about the theme designers here, they're very helpful and eager to ensure you their theme works fine. If you may bump into any trouble, they be more than willing to help you out.