I'm not current on usage of 20 amp plugs.
I wired our house with what I think were "standard" 120V AC receptacles throughout but using 12 gauge wiring and 20 amp breakers. Out in the backyard our motorhome's air conditioner starts and runs just fine through a heavy duty 50 ft. extension cord plugged into an outside 20 amp fused receptacle.
Where does one commonly find NEMA 5-20 plugs/receptables being used nowadays as opposed to NEMA 5-15 plugs/receptacles wired with 12 gauge Romex wiring fed through 20 amp circuit breakers?