Maybe, but the extremes you quote may change the aerodynamics, so maybe not.

Probably too difficult to measure an aero difference. The main thing is how long you can maintain 300 watts at each cadence.
There is a link between power and cadence though. Generally higher power needs a higher cadences at the expense of efficiency.
For example. If I do a 10 km TT. I pedal at 90 rpm and 300 watts. For a 40km I'll do 280 at 84 rpm.. average.
This will vary for others and is a very broad example.