While I have not gone through the Amsterdam interviews, I have gone through interviews in SEA. Here are some tips to address your concerns:
1. You can consider asking the recruiter, or reaching out to McKinsey Amsterdam folks to ask about this. Most of them should be happy to answer! However, I'd guess that the majority of the interviews will be held in English - since you will be working on projects outside of Amsterdam / the Netherlands that requires communication in English - you may still want to check with the relevant personnel!
2. Typically, I notice that cases can be (to a small extent) location-specific. It'll be good to understand what are the key industries / companies that the McKinsey Amsterdam office works with. Also, it could be practice-specific. So say for example you are applying to Operations, then there will be a focus on more of such cases. However, most of the time, you will not be able to predict and prepare for such cases since it could be assigned at random from a database (especially for Round 1). So it's more important to practice structuring, identifying insights etc., as compared to preparing for industry-specific cases.
3. Again, you could try networking with a few McKinsey Amsterdam consultants to better understand the nuances and the culture in the office there. Also, feel free to participate in their external events (for students, professional hires etc.) Glassdoor is another great resource to check out!
Hopefully, someone who has been through / knows the process better can share here too :)
Good luck for your interviews!