There are still effects even with Render Effects turned off, and "Compatibility Mode" doesn't get across that it's for low-end systems. Perhaps they could be changed to something along the lines of Advanced Effects and Lightweight Mode? Another option would be to drop the advanced video options menu. Render Effects and Compatibility Mode are mutually exclusive, so we effectively have another low-medium-high choice in the advanced video options; this could turn into an "Effects Quality" slider next to the Graphics Quality one.
What settings work best for those of you with lower-end systems? Is anyone using Render Effects without high graphics quality or Compatibility Mode without low? If not, it would work to roll those options into Graphics Quality. Something like "Very Low" for low-quality with Compatibility Mode or "Very High" for high-quality with Render Effects.
The basic functions are outlined on the Wiki.