2017 Volt owner, myself. I have driven ~8k miles in my Long Range Model Y. The Volt Wh/mi for the EPA rating was 267 Wh/mi. I am at 269 Wh/mi in the Model Y overall for 4 seasons for two years.

You are still new to driving the Model Y, it takes time to learn to drive smoothly for maximum efficiency. The regenerative braking in the Model Y (no longer user adjustable for low regen, only standard regen is provided) is much stronger than the Volt’s regenerative braking even accounting for driving the Volt in L shifter position. Over time you will learn to feather the accelerator pedal rather than fully lifting your foot. When accelerating you will find that you don’t need to apply much throttle for daily driving and still pull well ahead of most of the other vehicles from a stop light.

Tire pressure: Be sure the tires are fully inflated to the recommended 42 PSI (as measured cold in the A.M., not in direct sun.) I prefer 44 PSI cold tire pressure with the OE Continental Procontact RX tires.

In Florida you would see some improvement in efficiency (lower energy consumption) if you have the windshield and other side glass tinted with a good ceramic tint film. The roof can be tinted but the benefit over the factory IR and UV treatment that comes with the roof glass makes less of an improvement over tinting the other glass surfaces. Do get a sunshade for the glass roof. (Tesla sells a mesh fabric sunshade or you can find a large selection of one piece and two piece sunshades for the glass roof.)

When I drive on the highway I observe 260Wh/mi or higher depending on speed and use of the climate control system to stay warm (not an issue where you live.) 280Wh/mi is fine considering there may be a slight head wind or cross wind.

The Tesla data for the EPA combined city/highway range estimate does not include driving over 45 MPH and there is no use of the climate control system for heating or air conditioning. The only way to drive the Model Y and get close to the EPA estimated range or Wh/mi figure is to live where no cabin heating or AC is regularly needed (HVAC fan only) and drive at similar average speed, i.e. under ~50 MPH, on flat terrain with no head wind or cross wind on dry roads. For many, depending the wheel and tires used the Wh/mi can be expected to be between 250Wh/mi and 300Wh/mi with ~270Wh/mi being a consistent result for many Model Y drivers. For every 5 MPH that you lower your highway speed you would see an increase in efficiency and range of almost 10%.