From what i’ve heard BD works in the simple way that if they dont think you’re ready for the world class corps they’ll tell you to audition for BDB which isnt a bad thing. Open class is a great place to start if you’re looking to understand the DCI experience before you commit to traveling half way across the country to audition for your dream corps.
and it’s fine if you arent currently at the level, corps usally pick flexible people. and by flexible i mean willing to learn. because its almost a 100% chance youll have to change your technique to conform to theirs and as long as you have experience and can learn you have a shot.