I have tried to measure current between VM and ground, (with VIN = 24V) the result is 23.3-23.5V, So I think that when current flow back to source, some of power will loss due to this voltage different.
Also, G2 driver current limiting is not accurate at low current. It means that G2 is designed to drive high current motor.
For some reason, I happen to find high voltage motor(36V+ with approx 3A current) easier than 24V, 5A.
So I think I need a driver that can set limit to 3A and drive with more voltage.
Also, about PWM frequency, I use a high-spec microcontroller that can output very high frequency so I would like to run at highest frequency available.
I am not sure about this, but I think PWM frequency and current is a trade-off.