I would suggest that you may be mis-interpreting things or it might be the way the user interface is presenting power information to you is misleading.
Plugging in AC power should not suddenly make your CPU start drawing more power, that would just be silly. But the GUI may simply be indicating to you that, with AC plugged in, your potential CPU performance is higher should you require it.
As for the ventilation going while AC is plugged in, that's almost certainly due to the battery charging (charging causes lots of heat to be generated which in turn can cause the laptop's fans to turn up a bit).
The other thing to look for is some kind of hidden advanced power settings especially within Toshiba's own Power application, whatever it's called. Toshiba's own application will have far richer configuration than what you find in Windows' control panel.