What I had planned to do in my new home build is use a duplex 5-15 (at least 2 such circuits, if not a separate circuit for each duplex) on a 20 amp circuit, but also include a single 5-20 next to it. The idea is to have at least 2 circuits that 20 amp appliances cannot use (so the capacity is available for multiple smaller appliances). OTOH, a separate circuit for every outlet would eliminate the complication and you can plug a 20 amp appliance anywhere without worry that plugging a 5 amp appliance somewhere else will cause an overload on a circuit.
