"Smart" is difficult to define in terms of animals. I've worked with hundreds of Thoroughbreds and while they aren't "smart" in the sense that dolphins and apes are smart, they are highly perceptive to any changes in their environment. Race horses are trainable athletes, so in that sense one could say that they are teachable.
The Jockey Club, the registry for Thoroughbred horses in the U.S.
A thoroughbred/quarter horse X is called an apendix. They cannot race on the track, but there is an apendix registry. I wouldn't say that all apendixes show the good qualities of both breeds; on the contrary, I think that many show off all of the bad traits.
You can get a copy from the Jockey Club, which is the American Thoroughbred registry. There may be a small fee and may be able to download which will save time.
Appendix.
Files called "hives".
A Thoroughbred is a registered breed, while a Thoroughbred X (literally 'Thoroughbred cross') is a mixed breed with Thoroughbred blood present.
Look around and when you see a horse farm ask them if they know anyone who has any for sale. Most people with horses know others with them too! A chestnut (A.K.A Sorrel) horse crossed with a cremello will always come out with a palomino foal.
Thoroughbred is also a term for a dog or cat of pure breeding. As an example, a poodle is thoroughbred when he is the offspring of two poodles of pure poodle bloodlines.
A registry file, or most would called it "Windows Registry" is a database that stores hardware, software settings and options of Microsoft Windows Operating System.
hives
Hkey_classes_roothkey_current_userhkey_current_confighkey_usershkey_local_machine
it's called stud fees, when you pay a stallion's owner to cover your mare.