Well, there is "commercial" as in "not a passenger car," and then there is the other "commercial" as in requires a CDL and compliance with interstate trucking rules.
When someone says "commercial," think truck plate. I actually saved money on insurance in high school by registering my VW bug as a "commercial" pickup truck. The previous owner had cut the back of the body off, and covered the engine and bus transmission with a plywood box that looked like a pickup with a tonneau cover. Ah, those were the days!
In NY, almost all pickups were required to have "commercial" plates until recently. The exception had been that only personal-use pickups with permanent seats or sleeping facilities in the bed could be registered as passenger vehicles. Very important downstate, as only passenger vehicles are allowed on the parkways, which usually move more smoothly than the "expressways" (Interstate highways). Ticketing pickup trucks with passenger vehicle plates for "improper registration" used to be "low-hanging fruit" for police officers.
Now, the law was changed so any pickup used personally and not in support of a business or trade, and not marked with a business name, has the option of being either a "commercial" or "passenger" vehicle here.
The CDL-type commercial follows Federal designations:
Under 18,000, not "CDL" commercial unless it is a "bus" with over 14 passenger seats
Class C - straight truck/bus 18,001-26,000 lbs, with trailer 10,000 lbs or less
Class B - straight truck/bus 26,001+ lbs, with trailer 10,000 lbs or less
Class A - tractor-trailer or truck-trailer combinations
So having a 10,001 lb. vehicle with "truck" plates does not make you a CDL commercial operator subject to interstate trucking rules. You are 'non-commercial' if not operating in support of a business.
The best thing to do is to check out the local quirks. Go to the RMV website, grab the brochures from their lobby, or if you see a trooper at a truck check point, stop (in a car) and politely ask for his/her understanding. Don't ask the cop on the corner who does not deal with CDL vehicles all day.
Edit: I had skimmed over your middle post that you already had your RMV answer on the type of plate to use. But you are still "non-commercial" commercial if you don't have too many seats.