You can look at the American Brittany Club website or magazine and see who the breeders are of the winning dogs, including nationals, if field trial stock is of interest to you.
One of my dogs is from field trial stock. He is an athlete and hunts hard with a lot of endurance. He hunts every waking moment that he is outside. This can be a pain in the ass. In the house he is fine. Put him in the back yard, he is hunting. When hunting, he will easily get out 400 yards and then some if you let him or want him to. He isn't hard to reign in, but he will get out there.
My other dog is from a breeder that isn't heavily into field trials. They do some, but it isn't their main focus. They do have some good hunting lines, though. This dog is mostly a 200 yd and in dog, and he checks in regularly. I can hunt him for 3 days and not use the collar, whistle and voice only. He has a great nose and hunts his ass off. He is chill in the house and in the back yard and when walking in the neighborhood. He isn't on every moment he is outdoors. He is on when he needs to be, though.
When quail hunting, the field trial stock dog is great for covering a lot of ground. When you are trying to round up singles, the other dog shines. They are a pretty good pair.