@jeanmilost
I can't answer all your questions, as I'm not an expert on Qt's Model/View system, what I do know is,

that all models have a QAbstractItemModel as base model and that is also the ABI for all views.
For that reason alone, you can assign all models to all views. You will however not get a useful representation of all your data in all views.

As I understand it, and anyone fell me to correct me here, the other higher level classes of models are only there to make your life easier, as in you do not have to implement all functions/functionalities of the whole AbstractItemModel class