Wow, Openboard is a huge keyboard by default with lots of vertical key spacing. It also has two of my favorite Gboard features:
Swiping left and right on the spacebar moves the cursor left and right.
Swiping left starting at the backspace key will highlight text, then releasing the key will delete the highlighted text. However, it doesn't pop-up the deleted text as a suggestion to let you undo it, in case you didn't by accident.