The whole point of contact and keeping horses head down is to promote relaxation in the ring, and holding a horses head down with leather and metal doesn’t mean your horse is relaxed. It means you’re forcing their head down. But then again, I’m not a trainer, and it may depend on the horse, but over all no.
no, just no. the horse learns to brace off them, they cause the horse to break at the poll & build incorrect muscle. they force a false frame. you can accomplish the same thing without them, why waste money on something that does it incorrectly?
I dislike them. They are very rarely used correctly, leading to an incorrect outline. A lot of people who use them think "on the bit" means sticking their head down, but in reality, it means coming up from behind, and working through the back. If this is correct, the head will naturally carry itself. You will notice that those with draw reins often have what you call a broken neckline. A horse can also have its head where it looks as though it's correct, but the back is hollow and the hindlegs don't come underneath, coupled with tension along the neck. They're a lazy rider's tool, most often (in my opinion) used by the ignorant or those who don't bother producing their horse correctly.