The NKBA does address cooktop or range ventilation. The IRC (International Residential Code) requires a minimum of 100 cfm for a ventilation system vented to the outside of home. NKBA recommends a minimum of 150 cfm. But if a larger cfm figure is needed, NKBA recommends a properly sized ventilation unit vented to the outside of the home. In addition, the IRC requires that all instructions be followed during the installation of any appliance.
I would suggest you contact the manufacturer and see if a ventilation unit is required for your specific range. If so, ask about the minimum cfm required. Then, to meet the code, the ventilation unit must be sized to meet the manufacturer’s requirements. However, your unit may not require a ventilation unit. If this is the case you are OK with the OTR installed. Even if a ventilation unit is not required most people want to rid the kitchen and home of unwanted heat, odor, steam, smoke and grease. Since cooking habits vary greatly the cfm can vary also depending on your use. If you typically use all burners and the oven at the same time you may want a ventilation unit with a higher cfm rating to remove the heat alone.