Good question, there are things that are almost always similar in McKinsey case studies and things that typically change, making the cases offered a very good reference in terms of what to expect yet not cases to memorize as is.
1- What is similar
The structure of the case studies tends to be similar across interviews. It typically starts with the given, followed by 1-2 conceptual structuring questions, followed by ty 1-2 quant and exhibit questions a recco at the end. In some cases and if time allows, there could be an additional question (conceptual or analytical).
2- What changes
The given, problem statement and topic change from one case to the other. However, as long as you're familiar with the typical structure, know how to breakdown your answers and run the math, you're good to go.
Conclusion: do memorize and get used to the typical structure of cases. Learn how to conceptually break down the ask, how to crunch numbers, read and analyse exhibits as well as give your final top-down recco. However, expect a variery of topics and situations in the actual interview.
Hope this helps!