Oil Viscosity and Oil Change Intervals

I recently started doing my own oil changes and basic maintenance on my 2019 Prius after my local dealers all started experiencing staff shortages and the appointment times became untenable. As a happy side effect, I'm now learning a lot more about my car and automotive maintenance generally.

I notice that the owner's manual specifies that 0W-20 oil "can" be used on a 5,000 mile oil change interval, but that 0W-16 is preferred and may be used with a 10,000 mile oil change interval. Confusingly, the manual also states that a higher viscosity "may" be better in extreme conditions or at high speeds.

I live on the Gulf Coast. It gets pretty hot in the summer, and rarely gets more than a little chilly in the winter. I drive about 20,000 miles per year, but almost all of that mileage is done on a handful of very long road trips at 70+ mph (last month, I spent over 3,000 miles on a road trip and less than 100 miles running errands near my home).

Does anybody have a strong feeling about whether 0W-20 (or some unspecified higher viscosity?) might be more appropriate than 0W-16 for long road trips in the Deep South? My concern is that a 5,000 mile oil change interval with my driving pattern would basically mean throwing away brand new oil after each road trip.