How to determine the correct 12v relay
It's okay if you use a car relay as long as it handles more current than your load, you'll have the advantage of having terminals to easily connect all the wiring but it will cost you some more current when the relay is on, car relays can draw up to 2amps from your battery, so that is something you should keep in mind considering your load only draws 600mA.

Using pcb relays will work as well and draw much less current, but they're hard to connect if they're not soldered on a PCB