DOS:2 EDITOR[/url] ideally provides the depth I believe you've enjoyed NWN.
Whereas the GM mode is more entry-level tool that also requires less preparation. I'm hoping it will still be reasonably deep.
NWN has pretty strong editor and GM mode. Those two functionalities are completely different. Different tools, different UI, for different type of user.
GM interface could alter current game, could add placable like a tree or a treasure chest. Or direct control a creature. Changes in the world made by GM interafce are temporary.
By Editor you can program or set each and every element or setting. You can attach a script to any event of any object. Changes made here are permanent.
However, good controlling GM interface require a skill. Diference between two GMs in NWN was HUGE depend their skils. Also, when you get skilled in NWN editor you could be lost as GM. Different things. I hope that Larians take NWN and play game/editor/GM for weeks to learn.