Just a quick comment, as I don't have much time. But it was mentioned about the Jazz line - that line is known for being more than a little hot and flighty. Just as the Ferro line is known for being difficult and sensitive.
As with any breed, you'll get lots of different results from different crossings. But like rumba mentioned, these are not bred to be pleasure horses - for the most part they are bred to be high quality athletes. There are definitely some lines that are more for professionals and some are more amateur friendly.
But there is reason that KWPN and Hano compete, every year for 1st and 2nd spot in both dressage and jumping.
*Riding is not a sport, it is a passion. If you do not share the passion, you do not know the sport, and therefore are wasting your time*