You should choose a meter rated the same or higher than the circuit breaker protecting the load to be measured. You may make an exception to that rule if you know that the total load on the circuit will not exceed the rating of the meter.
You can use a meter higher than necessary and it will work fine most of the time. However it will miss small currents that a properly sized meter would measure. We guarantee that the meter will be accurate within 1% over a 100:1 range. That means a 200 amp meter will be accurate between 2 amps and 200 amps.
In California, the state's power meter regulations require that the meter be accurate at 5% of the rating of the circuit breaker or cord used in the system.