My experience with EPA-compliant low flush toilets is not good. I and everyone I know considers them to be "multi-flush" toilets because you have to flush 2 to 3 times to clean the bowl out. A better system is those valves that have a smaller flush for "liquid-only" and a larger flush for "solids" but even then you need a tank that holds at least 2.25 gallons.
EPA-compliant toilets are so bad that I shop for older toilets with larger tanks when I build a new home or remodel. I just tell the builders to install the cheapest thing they have for the inspection and then I swap it out with units that actually work.
