On whether Step 1 questions are the same as CBSE questions, if you don't think they are, we'll have to agree to disagree. That's definitely just my opinion though, based in the logic behind it. NBME designs the CBSE essentially as a "practice test" for the Step 1. Many medical schools actually require their students to take the CBSE in order to prove they're ready for Step 1. With that in mind, and also with the fact that NBME designs them both in mind, I believe they're the same questions. *yes, this is opinion, and I have not seen any evidence in favor of or in opposition to this - I have only seen and only offer conjecture*
It's a moot point though - I think we agree that preparing for CBSE as if it were Step 1 is a good life decision.