Elementary OS is better than sliced bread but there are just a few small niggles one of them is that the power settings are consistent between charge and battery when it would make sense to separate the timeouts; eg you want battery screen off to be MUCH shorter than under charge. Thus brightness, auto brightness and Turn Off display should all be moved to the Plugged in and Battery panel IMHO does anyone agree?
You have the option to dim the display automatically when you aren't using it (on battery).
Also you can suspend your laptop automatically, saves much more energy than turning the screen off, and it takes just a few seconds to load everything again.
Brightness has nothing to do with plugged in / battery so it's good where it is now. I mean, you change the brightness when you can't see the screen well, don't you? It has nothing to do with the power input.