Teams is (at least for now) a special beast
. What we did learn already is that files that are stored in a team are protected as long as the O365 group (underlying mechanism for teams) is protected and its subcomponents (as you said: the SharePoint site). However, what we (probably) won't have is that you can restore the files (that you will be able to do obviously) but they won't be visible in the team again (unless you add them manually again). MSFT does not give us API access yet to the data that says what content a team is made off (with links to the files/ chats/ tabs/ whatever...)
So backing up the data yes, restoring also, visible again in teams... Only after manual insertion again.
For licensing: We will license per user (same as MSFT O365 licensing)