regarding the power suply differences between models...
ALL XBOXs be it 360 or legacy have issues with heating/ failure, and even fire. Even the first gen XBOX has an issue... We literally had units(legacy) smoke in the automation lab and shit and had to switch them to a newer PS wityh a breaker in it (that didnt intitially come with the units)...
The 360s we used atr MS were of two different varieties... The dev units were actually different than the retail units... used different powwer supplies, and actually had serial debuggers (that would generate debug spew) when broke, code failed etc, for debugging and fix implementation. The retail units used a smaller "brick" with different output... It was an attempt to not only make them run cooler, but make them more effecient (whaich as a by product made them run cooler).