Several weeks ago I ordered the Brydge 10.5 keyboard to use with my iPad Pro. The keyboard is aluminum and when you close the iPad onto the keyboard it is a little larger than a MacBook.
You slide the iPad into a pair of hinges that holds it so security that you can lift up the iPad and the keyboard does not fall off. To remove the iPad you have to hold down on the base and pull the iPad up, and while snug, it is relatively easy to remove.
The keyboard is the same size as the iPad Pro 10.5 in landscape, so the keyboard is large enough for touch type but it is smaller than most notebook keyboards and feels cramped. While the letter and number keys appear to be “standard” size, all other keys like shift are slightly smaller. Bottom line is that the keyboard takes getting used to, is serviceable, but if you want to type for hours you might want to use a larger keyboard.
A definite advantage to the keyboard being aluminum is that it is lapable, so if you are the type who frequently types with a notebook on your lap you will like the Brydge. I imagine that the the 12.9 inch version of this keyboard, which is designed for the “original” iPad Pro 12.9 is nearly perfect.
The Brydge keyboards are not the cheapest, but I think if you travel and seriously need a keyboard, this is the one to have as it is likely very usable in an airplane.