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.
I've known many very quite TB, in fact, I own one. They do tend to be a sensitive breed though. I also know great, quiet ponies and, while suggest an arabian for show hunters, I've known plenty of quiet ones. I think I would suggest a warmblood. I've known many that were very calm and quiet to ride, though like all breeds this is not true of all of them.