I have the 12.9 " Pro. After trying and returning the Apple Smart Keyboard twice, I decided to stick with the Apple Magic Keyboard which I love. But I needed a good solution to transport the IPad and keyboard so I just picked up the Waterfield Designs sleeve case. The Magic keyboard fits perfectly in the outside pocket and it even has a little pocket for the Apple Pencil. I like the versatility of the external keyboard plus I love typing on the huge onscreen keyboard as well.....
https://www.sfbags.com/collections/ipad-cases/products/ipad-sleevecase
https://www.sfbags.com/collections/ipad-cases/products/ipad-sleevecase