I have a couple of the earlier GTX-500 outboards, and mine have shaft drive and bevel gears in the lower unit too. I was under the impression that the newer ones had bendy cable drive, but your link says otherwise.
The GTX-500s are pretty powerful, by my standards anwyay, and with a BB 850 motor in the back the ones you mention just have to be fliers! I'm pretty impressed with Graupner engineering, very little has gone wrong with mine, just needs a little grease and brush lube on the motot.