The well-resolved model (3NF / BCNF) provides the best average performance and the least number of modification anomalies for the largest number of scenarios. It's big, so I'll start from there. Since your requirements are fuzzy, this seems like the most reasonable option.
Actually, the most reasonable would be to revise the requirements until they become more "clear";)
In addition, if you can get some early extracts from your data provider, you can experiment with it and get an idea of the distribution of data (not all people live in one country, and in some countries there are more people than others Not all people have children, and the number of children per person is very different depending on the country). This is an important point, and it is very important that the optimizer can make the right decisions.
Other than that, I agree with everything that Walter said, and also gave him my vote.
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