It will feel like some one is pushing on your teeth. The brackets stick out a bit from your teeth making it feel like you have a full mouth of metal, big lips and your bracket may rub against your lips feeling again like a metal file.
While some breeds may be more suitable than others for a beginner rider, there are always exceptions to the rule. Quarter Horses often make great beginner horses because of their even temperament, but some can be quite hot or energetic for a beginner.
A beginner rider is wise to choose a horse by its temperament and training, rather than focusing on breeding. Older horses of any breed tend to be more predictable than younger horses, and no matter what the breeding, an un-broke or 'project' horse is always unsuitable.