We also took the basic science NBME . . . and yes, I think the actual Step 1 is closer to that than to Q-bank. But don't let that dissuade you from using Q-bank. I know lots of people who only used that, were scoring in the 70s or so, and did quite well on Step 1.
Bottom line, nothing out there is perfect in terms of preparing for the test. There were days when I did in the 50s on Q-bank. There were questions on the USMLE that I hadn't encountered in ANY of the 10+ books I used.
Best study method, I've found, is to think CRITICALLY during studying - question everything - why is it wrong, understand the answers, etc. Simulate actual test days as much as possible. These methods, in addition to using the "tried and true" such as First Aid, should be sufficient - regardless of what other sources/questions you do.
Be confident. You wouldn't have gotten this far if you couldn't handle it. 👍