Ours only used ground nest boxes, so I would go with those. Wood ducks and Mandarins are a little different in that they usually nest in trees, so that's why they prefer mounted (raised) nest boxes.
Oh, and I don't mind the questions! I'll help in any way I can. Laysan Teals may not be the...
I used to breed them back when I was a zookeeper. I didn't know people kept them as pets, they are critically endangered in the wild. Are these yours? They can absolutely fly, so if they are allowed to free-range, or stay in an enclosure without mesh over the top you'll need to clip them...