Actually, it's the other way around. The RAF fighters are equipped with constant speed props and automatic boost control. That means you can set your RPM and forget about it.
You can also set your manifold pressure and the auto boost will maintain it steady despite altitude changes (at least as long as you're not so high up that it can't due to lack of ambient air pressure).
Of course, if you go to coarse pitch/lower RPM the manifold pressure will rise and you'll need to readjust it. However, the overall recipe is:
1) experiment in free flight and find the highest power setting you can run with the lowest radiator use without overheating
2) set it once upon entering combat and forget about it, unless you need to chop throttle in an overshoot situation or something similar
The 109 on the other hand has neither of these systems. Manifold pressure for a given throttle position will vary with altitude. The RPMs also vary with airspeed, manifold pressure and possibly attitude and G-load and you have to "dance" on the pitch controls to keep it where it should be.
That being said, i find that taking the time to get used to it in free flight (seems like this is a must for me on every aircraft
) and getting used to how each RPM band sounds, i can easily keep it within limits and maintain optimum RPM for whatever it is i'm doing without looking at instruments.
It's like shifting gears in a manual transmission car, after a while you do it by engine sound and sense of speed
