I'm going to suggest you keep the 3 blade prop, for the following reason.

As Hydro Junkie said, the engine is a little difficult to keep tuned. To make that less important, run the engine at high speed. Then high air speed will be a problem, unless you use an inefficient prop - so use the 3 blade item.

With that setup, you can learn about tuning the engine. You can run it wide open (as new folks tend to do) without reaching such high speed that you don't have time to react.

And, actually, using the flaps (to keep your air speed down) is not such a bad idea. When you're more experienced, you can put the flaps up and put on a more efficient prop, and the plane will go faster, but at the moment that's not the objective. First, fly like you want (wide open throttle), use the flaps & brakes & inefficient 3-blade prop to keep your air speed down, and you'll have a better chance to learn things.

Good luck,
Dave Olson