Actually the electrons have further to travel which increases the resistance and reduces the efficiency. Over the lifetime of the MBP we are talking hundreds of gigawatts wasted.The cord is just an extension. If you want a longer cord, remove the pins on the power supply like that:
And connect the extension cord instead. Most people I know use the extension, but you may prefer not to use it for more portability. It's just a matter of how long of a cord you need, it makes no difference on charging itself.
That's terribly exaggerated. Your MBP itself will probably never use a full megawatt during its lifetime. Waste because of the extension is negligible. Charging time is the same.