I haven't installed the beta but based on the announcements here is my take:
- I still don't think that each app will be able to access the same files and folder structure on the iPad (a showstopper for me)
I don't know exactly what you mean by this but one can already have a folder in Files.app which opens apps (no default apps so one needs to go via the share button, which is cumbersome) directly from Files.app. Take Word for example, I can store a Word document in a folder in Files.app and open it in Word without having it make a copy. Instead, it reads directly from the folder and saves to that folder not making any duplicates.
This was added either in iOS 11 or 12. However, all app developers need to add support for it to work so maybe that's why it is not well-known yet.