How important is your stride in pitching?

Does it effect how fast you throw?

For someone my height and someone who is very lanky should my stride be long?

There’s no absolutes - always exception. But, in general, a longer stride implies you’re doing some other things right like maintaining good posture and balance, creating good momentum, and taking care of the glove to stay closed and rotate late. These things all affect velocity as well as arm health.

As a “guideline”, shoot for a stride length of 6-7 of your shoe lengths. But if you’re not there, focus on those other things I mentioned above. Stride length is a result of those things so improve those things and let stride length happen.