well servo wire is all the same size, the plugs are all the same. it doesn't matter what you plug into the the servo its still only going to take so much. I check my batteries after every flight and the simple answer to your question is to isolate servos from your receiver. I run one pack for the receiver and the servos have there own battery. 7.4 volts is plenty for any application, Ions, A123s, Lipos they can all push out more that anything I have ever flown. 40% and below that is, after 25 years I have never lost anything due to power loss from overloading my setup.
Not bashing all this tech stuff by any means i think it is cool you guys can make sense of all that.