Both Tesla and Tire Rack say that a 255/40R20 is the tire size. Tire Rack shows a few options for wheels - and I would recommend you pay attention to what they say as they guarantee that their combination will fit correctly without rubbing.
And by anyone's definition, a 40 series tire is low profile. If you want to go lower you'll have to go larger in wheel diameter, and according to Tire Rack, you can't do that without modifying the vehicle.