I also live in NYS and i have two maxis registered as Class C. when i went to register my last one the woman punched in the VIN and the system told her it should be a class B and she asked if i had insurance. I said no, and said that it should be a class C because i already had one just like it registered as a C. She then pulled out her binder of regulations, asked me how fast it goes, to which i promptly replied "20mph" and she says "well, i guess I'll have to believe you" and she handed my my plate and i was on my way.
all that aside, even though i'm not required to wear a helmet, I always wear a fullface. as far as insurance goes, I don't have insurance, and that's the main reason i chose to register as a class C. I live in a small town and don't ride very far, or in heavy traffic, and If someone hits me, and i'm not required to have insurance, it's their insurance that pays for the damage. If something else happens to my moped, i can pay to fix it without worrying about whether or not my insurance will cover it. and if i hit someone, which is definately not going to happen, it's pretty likely that the damage to the other vehicle would be negligable.
my last moped (a sebring) i had to register as a class B because it said top speed 30mph right on the vin plate, and the insurance only cost me $75/year, so if you gotta get insurance, it's no big deal.