If the capacity plate on a vessel gives the max persons and max weight does one override the other so you can have a person or two over as long as your not over the max weight of plate?

The max # persons is a recommendation based on the assumption that the average person weighs 165 lb or so - most grown men are over that. Stick with the max weight, but don't forget that # includes all people/supplies/equipment/fuel as well as the motor assembly and steering control.