According to this Nebraska statute, it all comes down to whether the vehicle is being used primarily for transporting persons or property for compensation: https://nebraskalegislature.gov/laws/statutes.php?statute=60-316
Every state has a statute defining Commercial Vehicle, and they're all...
Understand, once your box van is registered as an RV it is no longer a 'commercial vehicle'. Any officer trying to give you a ticket should be shown the registration.