If by templates you mean the “Rolling Template,” “First Person Shooter,” or “Flying” templates that the beginning of the videos start with, then Unreal Engine comes with those directly, not the plugin. You will then need to use those as starting points and follow the video tutorials, the blueprint does not come with the above tutorials already prebuilt.
For a better understanding of the orbital mechanics data, like true anomaly, eccentricity, etc. Wikipedia is probably your best bet for all that, it does a better job explaining those concepts then I could. I’ve also find this open source textbook helpful: https://books.google.com/books?id=O_7TCgAAQBAJ
Finally - you could technically use this blueprint for a cannonball trajectory/arc type functionality…but why would you? The unreal engine physics engine can do that more efficiently than a blueprint plugin. Unless you want gravity to vary as the cannonball gets further away from the ground…which is really just another way of describing an orbit 