Well I tried modifying the config.wtf for each of my clones, and changed the window size from 800x600 to 960x600. WoW Maximizer still resizes my windows to 960x585, but the graphics are still rendered much more accurately.

I would guess that WoW chooses it's rendering "aspect" based on the resolution selected in video options or in the config file at startup, and sticks with that aspect no matter how you resize the window. If you start off with your window in a 4:3 aspect but resize it to a 16:10 aspect, the graphics stay at 4:3 and distort horribly. Only when you select a new resolution in video options will WoW recalculate the aspect of it's rendering.

This probably means that if you want undistorted graphics for a really wierd window size, say 500x500, you should probably set your config file to 800x800 (based on minty's observation of WoW not accepting less than 800x600).