24V , give or take a few volts isn't a problem. Most heavies are running 24V motors on 36-37V.

Yes, you'll need a kind of variable voltage regulator. Called an electronic speed controller.
That makes it possible to vary the voltage to the motors from 0 to full voltage from the batteries.

But 30 amps no load. That's a lot. Is that the 3 together or just 1?