My understanding is it's the motor that sets demand based on speed, load and other factors. Its the esc's job to supply. You match the esc to the motor.

I've messed around with an onboard data recorder on my Slash that I run with 2S 5000mah 25C IP lipos with a MM/5700 Castle combo. There is a big diff in what the lipo can generate based on its C rating and what the recorder shows the system is using. A typical bash session in my backyard, recorder over a 8 min part of the run showed an average amp draw of 18amps. The highest amp draw was a 114amp spike and there were several other spikes that were above 100amps. There were plenty od draws in the 40-80amp range as well. But with coasting, or running at constant speed, tha average is pretty low.

I prob could do with a lesser lipo since the burst rating could prob cover the amp spikes, but I wouldn't want to push a lipo harder and have it run hot. This lipo comes out after 25min just barely warm. Thats the setup I want to run - one that keeps everything cool.