Yeah, those low-kv motors are heavy, that's just what I wanted to show. The Neu drive with gear seems to be well suited, maybe even a bit too powerful. You see, 1300 motor kv divided by 6.7 gear ratio gives 194 drive kv. That's a bit more than the AXI but the recommended props (about 20x14) would even fit. And I think you would find a matching centerpiece for the 10 mm prop shaft.

An efficient propeller needs a low power loading, that is Watts power per square meter prop disk area. The slower the plane flies the lower the power loading has to be. You may read about the theory [link=http://www.mh-aerotools.de/airfoils/propuls4.htm]here[/link], especially the second picture (diagram) about optimum efficiency. Compare a prop drive to a jet engine: the jet has to accelerate a small amount of air to high speed to get the same thrust as a propeller which accelerates much more air to much less speed. The latter is more efficient, same airspeed provided.

According to the theory, you have to choose a big enough prop disc for the power the airplane needs for climb and for the intended airspeed. If you choose a too small prop disk you need a stronger motor because more power is wasted, and that is done by turning faster. So you can't compare to different kv motors on the same prop. The high-kv motor would have to be much more powerful two turn the same prop with more rpm. The bigger the prop disk is for a given thrust needed the slower the prop has to turn. So for the same plane: big prop - slow rpm or small prop - much rpm (and losses). Sorry, this explanation isn't really thought-out.

Anyway, for cases as this one a motor-gear combination is virtually always much lighter than a low-kv motor. Don't even think about doing without a gear.

By the way, airbrake effect is well possible with a folding prop, no problem. It's just that the effect lessens with speed so it's more for glide angle control. And you have to test the effect before relying on it, maybe on another model. And you have to check that the ESC doesn't prevent it.