Each state has it’s own rules. Some use actual weight limits, some use a %. Of the towing vehicle. Some require break away switch no matter weight. Considering you are risking other peoples lives in a breakaway situation, think about the possible consequences of saving a few dollars.
Also, when in an emergency stopping situation, I have never heard any complaints about having extra braking available it is your choice but know that the laws vary and your insurance may not cover you if you are in violation of a state law.