You will need a breaker sized to the feed wire. If you run 10 guage, you dont want to be running a 50 amp breaker. I would consider running a 50amp with correct wire to your garage, and then a 30gfci out of another panel to your setup. Then you can have a bit extra for lighting, etc.
Otherwise you would be safer using a breaker rated per manufacturers recommendations, while also using correct wire.