I would agree with what everyone has said so far and won't repost.
I have two tb, one suitable for a beginner and the other, not so much. I would say that a majority of the ottb aren't good with beginners, but many who have never raced or been trained are usually just fine. My mare is the ideal beginner horse, but she was breed in Upperville, VA as a hunter and hasn't had a race horse in her background for generations, she is basically a big qh. Just thought I'd add that even if it a little bit irrelevant.