Given that the topic heading is "Servomotor Drivers" they are as good as the resolution you can resolve when servo driving them.
Achieving an average current that is somewhat less than steppers should be doable. as you only drive with the current you need to achieve the move or maintain the position.
Steppers on the other hand are driven at pretty much full current continuously (unless you have a clever driver that halves the current when stationary)
Whether you need heat-sinking or not is a function of the integral of the power they drive versus the waste heating dissipation capability of the device.
Whether it is doable sans heat-sink is an interesting question and depends on your drive train, duty cycle, loading etc etc.
Necessity hopefully becomes the absentee parent of successfully invented children.
