^ Head position clearly matters. If you tend to pedal head down, it argues for a shorter tail aero helmet.

So you need a helmet that works for you and your position on the bike. The right helmet for your fit and position is going to be an advantage, even if your position is less than ideal

if you’ve got a power meter you can figure out for yourself the best helmet for you using the Chung method. ( invented by a BF poster, who is likely your best source around here for aero info.) Only problem is you’ll have to buy or have access to the various helmet options to test.