Try to follow the WinUI 3 tutorials. You'll understand.

Could you elaborate please?

WinUI3 is awful for unrelated reasons. It's even a pain to use from C#, which is the language it (and the WinRT APIs) were designed to be the primary use case with. And of course C# namespaces work fine.

Newer Windows APIs are annoying to work with from C++, which is Microsoft's fault but signals something about direction.

I’m sorry, but this is very lazy non-answer.

If you have specific pitfalls to share, do so, otherwise what’s the point of commenting?