To be honest, watching lectures at 1.5x and reviewing with B&B is exactly what many of the students here do. That's what I'm doing right now to study for a midterm this week. The in house exams here still have to make sure they're covering what we should be learning for Step 1 so it's not like the material is widely different, it just might be presented differently or go into more detail. B&B gives great structure and good straightforward explanations of all the topics and concepts, and then the school lectures provide more context and details to fill in. I can only speak for Einstein but I would say that our exams are generally very reasonable and not difficult to study for if you give yourself enough time. Almost all the professors here provide syllabi for the lectures highlighting important topics, key words, drugs, and diseases, as well as practice questions, so it's very easy to formulate a study plan since they tell you exactly what you are expected to know. Since it's all P/F, you can prioritize how much time you want to spend studying with whatever materials you want and not stress about knowing every detail. I know students here who straight up don't watch school lectures and only study B&B and use the practice questions given to gauge their knowledge for exams. I personally would not let NBME vs in-house be a deciding factor in your school decision, I don't think it'll make much of a difference in the long run because you still have to put the work in either way.