In the end, you move your fingers in a smaller space so, when typing fast enough, it gets better than qwerty just because your fingers move less. If you have big thumbs it's better too because keys are bigger. I make less typos in this keyboard than in qwerty on touchscreen and I can type with a single hand fast enough, something I can't do with qwerty. But to each their own.

You can! You need to use YAML but you can edit your keyboard as you wish. I use italian layout (each language uses a different one depending on what are their most used keys) and added some keys for spanish letters (like ñ or ü)