The TB has definitely influenced the QH in a very positive way. It increased agility speed and refinement.
Cowboy I do however digress about the events of reining and cutting. Those foundation QH's could do the job and do it well. Yet as the events evolved they became more and more sophisticated and profitable. Demanding that the horses become more and more specialized.
I see this happening now in the Arabian breed.
The Qh stallions in the past were used for halter perfromance and racing before breeding. It was a good practice and essential to the developement of the breed. Now you have so many different types that breeding a Champion race horse to a halter horse would spell disaster. Shalom