No, the iPad layout is the same as before. The Duo is a new device and new format.

Pretty sure this is going to be TBD from Apple. No one outside of Apple would know the answer to this at this stage. No one has access to Duo simulators yet, so any design work would be in third party tools like Figma etc. So there's no way to actually get Duo screenshots yet.

iPhone Duo inner screen portrait will be like standard iPhone with tab bar at bottom and nav bar at top.

Have faced this issue as well & noticed that Apple system apps don't seem to face this issue, so unsure what methods they are using.