We are very similar in height and age, my weight is 130. The BMX bike you describe is how I set mine up and have no problems. My Haro is 21” top tube and a great rider but hard to manual. My 19” Mongoose is better for that. I don’t do wild stuff but enjoy riding all around Jax. I’ve only been on BMX for a few months too.

20” or 24”, both will work!