You have the general idea, yes.

As part of its installation, Easy Debian downloads one whopper of a file to either your tablet's internal or external card, your choice. That big file is like a virtual hard drive, and it comes with Debian and a number of popular applications already inside it. Easy Debian then performs various bits of magic that lets those Debian applications run from within the big file.

The big whopper of a file has been pre-made and tested by qole, and it's a non-trivial bit of work, so he can't easily create customized versions for different people. That said, he does accept donations on his web site, and I suppose a sufficient donation might encourage him to volunteer extra assistance.

If you do try Easy Debian, please proceed cautiously as you begin uninstalling and installing applications. For starters, there's only so much free space in the big file, and should that space run out mid-install, Easy Debian will become unhappy. Also, adding and removing Debian applications will cause other, supporting bits of Debian to be likewise added to, or removed from, the big file, and should those updates go too far, there's a chance Easy Debian may stop working.