Yea, differences between early variants were merely cosmetic. That said, I do believe there are different speed ratings for the motors. I've seen cases stamped both "25" and "30", on the variator side. I'm not sure what the actual restriction is, but it must be something more than just a spacer between the cheeks because why bother stamping cases with just that.
Later variants, namely the flat reed SLE and Sport had different wheels (7 stars vs 4), fenders, and other cosmetic detailing. Not sure about speed ratings for those years.