He was not a Gypsy Horse. Galway Warrior was a Drum Horse. Before coming to the US, he was owned by HM Queen Elizabeth ll in England. Sadly, he is gone now. And Gypsies are NOT necessarily 'vanners'. Only a few who happen to be registered within the Vanner registry. The term 'Vanner' was coined by a fellow in Florida, who happened to start a registry by that name.
In recent years, several very good Gypsies, have been sent to S. Africa. Drafts don't suffer from the heat, any more than any other breed. It's all about keeping them comfortable and with shade in the summer months.
When choosing a draft for riding, you would need to know the breed and be able to spot conformation faults, just as in any other breed. Incidentally, Gypsies, Clydes and other heavy horses are not necessarily 'cow hocked'. They have a 'set' which is quite different.