I think the key to smartphone keyboards is something like Nintype, two-finger swiping. It's incredibly fast and doesn't require you to learn a completely new keyboard layout to succeed.

It's also a lot more comfortable for one-hand typing since you can do multiple swipes per word.

Funny that looking at their "number of touches" and "distance covered" checker, I've tried a few words and thinking in my head how it'd be in Nintype and it would score far better than Keybee.

Unfortunately I haven't seen anyone since Nintype (and the older Keymonk) to give it an attempt.

Heliboard does two finger swipe! Not as well as nintype but very passable! https://f-droid.org/packages/helium314.keyboard/