There is a balance you should strike, between torque and RPM. Drift doesn't require gobs of RPM, but needs a certain amount to maintain the right grip/slip ratio for the tires to work properly.
You could go as low as 15T, or as high as 25T, but for your driving style, you will need to find that balance. If you are not overly aggressive, you could use a 15T effectively. If you are aggressive, the higher turn motors would yield better drift performance over the RPM range of the motor.

I am an aggressive driver, and the 19T and 21T work well for me.They don't equate to much top speed, but it's not top speed you're after, in drift.

And yes, the TZ is a 23T.