How do external storage devices work with the iPad?
You'd need a computer to do those things.

I.e. you're be able to load the image directly from the camera, and edit them in an appropriate app, but then cannot move the image to the external drive (at least not with another app that allows you to do that). You can transfer the image back to your computer using iTunes, or share it e.g. using Dropbox and access it from there.



Regarding NAS access -- this might be possible (again) using an app that connects to the NAS and allows you to browse and open files there. The iOS itself doesn't expose any file system to the user, be it internal or external.

You'd need to use iTunes Home Sharing to do this without any additional software, requiring the NAS files being added to iTunes and your computer to be running.



What's possible on iPad (and any iOS device) is rather closely tied to the applications available for it. The system itself doesn't expose a lot of "power-user" features like (gasp) file system access to the user.