They should focus only on the conformation of a horse unless otherwise specified in the name of the class, (for example some shows will have 100% color classes for paints and pintos). As for your horse, he will be judged first against all the other horses in the class and against the other horses of the same breed if there are some in that class.
You probably already knew that though.
"And somewhere in the northwoods darkness a creature walks upright. And the best advice you may ever get is: Don't go out at night..."