Question: If you need a readonly list for example a selectbox, which is better: A typed list based on two columns of 1 or 2 entities, or a dynamic list?

If the anwer is dynamicList, when should you use a typed List then? Because this is not really clear to me ...

Doesn't matter what you use, both do the job. The TypedList is typed, so if you want to use it in a typed manner, you should use a typed list. otherwise use a dynamic list. TypedLists also are easy to instantiate, dynamic list require code to set them up.