On the question re Templates in Planner, this has come up in two Office 365 courses recently. And judging by the traffic at UserVoice, it is a popular request. I added a vote!
Second screen capture shows templates topic in the In Development section of the Office 365 Roadmap – along with assigning task to multiple users and external guest access to Planner, both of which I have been asked about elsewhere
So this isn’t an answer so much as a “stay tuned for further developments”.