Countervailing story: the Ergodox (EZ specifically but that's less important) gave me permanent RSI in my thumbs, because it was too big for my hands, and to this day I pretty much can't use a keyboard layout that relies on lots of thumb involvement. Even just hitting the spacebar throughout the day or using my thumbs to type on a smartphone is enough to flare it up, almost a decade after I stopped using that keyboard.

YMMV, ergonomics are highly personal with respect to your body size and proportions. We didn't have the proliferation of keyboard layouts then that we do now. Perhaps if the Iris or Corne had existed then, I would still be using my thumbs for modifier keys in a 40% layout. I never got the hang of tapdance or hold modifiers.

The Atreus layout is the only one I can still use somewhat, because the thumbs are held closer to the hand rather than splayed out.