Dont really understand what you are trying to achieve

Do you want an esc that is smaller in physical size ?

Micro pro esc has less power handling capabilities than the stock traxxas esc

Changing the esc will not change the speed of the car assuming they can handle the current demands of the motor

Mamba Max with the Neu on 2s should be fine, change the gearing for more torque and less top end if need be

Cheers