No template is necessary to draw storyboards in Paper. Just draw in the upper part of the landscape canvas, leaving the tools exposed.
In Boardo, use one of the Paper Setup Presets. Boardo will automatically crop your image to roughly what you see above right. If you draw with this margin in mind, you'll find that your Paper boards look great in Boardo — and you can always tweak the framing using the Setup controls.
You can also draw in portrait orientation, and use Boardo to pan around the vertical composition.
Boardo also works with storyboards drawn in Paper on the iPad Pro.