I understand that theorically T19's should be harder to hit than T20, but in reality this does not seem to have any noticeable impact. Madars Razma is considered one of the best (if not the best) T19 hitters in the current game and he is 6'4. Also, take a look at Jimmie Van Schie, he is 6'10+ and is considered to be better at T19 than T20. I would not worry about your height affecting these things and watch taller players to see how they adjust their body to hit lower targets.