Yep, I was interested in drag racing physics for a long time, and it's basically wind speed vs horsepower.
Wind speed means your speed + headwind (so if you're doing 50km/hr into a 30km headwind, your bike acts as if it's trying to travel at 80km/hr, the same happens if it's a tail wind, 50km/hr with a 30km tailwind = your motor acts as if it's travelling at 20km/hr). If your wind resistance means you can travel at 50km/hr with 2hp (reasonable on a bicycle I think), then even if you produce 3hp, and you're in your highest gear, if you cant make it to your power peak, you never will go any faster, same with the opposite, if you're past your peak and don't have another gear to grab, you won't have the power to go faster anyway. It's strategic shifting to keep your engine in it's peak. Typically speaking, if your peak power comes at 7500 RPM, thats where your top speed should should be if you're geared right. Unless you're producing 3hp at 7500 RPM and you have up to 9000 RPM, and at that rev you're making 2hp, then if your gearing sets you at 65 at 7500 RPM and 75 at 9000 RPM, obviously the higher speed will need more power, but since you're beyond your peak, you're losing power. So logically your top speed will be in between 65 and 75, wherever your horsepower can no longer overcome wind speed. That's why you can go faster with the wind. Logically you'd think it's pushing you, but once you exceed the wind speed, you'll notice it's now become a headwind, and you're fighting it
Bonus question: how long of gear would you need, that if you were travelling away from someone, the doppler effect would produce the same tone as you accelerate away?