how do they get such fluidity in there bots!
Easy - you use control loops, designed to allow for continuous movement ... how to do this ? And you control the force the engine exerts, in order to control different variables.
You enforce constraints on the movement, on speed, on position, on acceleration and you adjust the engine speed according to what needs to be done. E.g. if speed is getting too high, reverse the polarity on the torque that you control.
(d/dt position = velocity, d/dt velocity = acceleration, d/dt acceleration = torque)
You change the torque immediately (ie just set it to some value), and you calculate the acceleration (voltage) sent to the engine like a1 = a0 + torque * (t1-t0)
Everything will move with a continuous acceleration, which is very, very smooth. To lower speed, set the torque to a negative (but NOT too negative) value. To speed up, set it to a positive value.
If you really want to impress people, do this type of control on the torque, ie one extra step. The advantage is that people interpret continuous torque as standing still. Ie you can move around in a room without triggering anyone's attention as long as you keep the torque of your movement continuous. This is very, very weird when you look at a robot arm.
You clearly see it is changing position, yet somehow you just can't believe that it's moving. You cannot tell when it stops moving (really, you just don't see it), you can't tell when it starts moving. It just fades into the background.