Regarding clipless sandals, here's my story. (I doubt I would wear them for strenuous riding, but obviously, as you'll see, I don't know everything.)

We call her Bronze Skin Girl. Mid twenties maybe. She's worn clipless sandals every time we've seen her. She's good. She's fast. She's gorgeous we think. We've never gotten so close to her to tell what make bike she rides, except it's black and has gold rims. Bronze Skin Girl is always ahead of us and never catchable. Once while we were filling bottles at a country park, she rolled by with legs like smooth polished myrtle wood. I don't know about your legs, DG, but if sandals are good enough for Her, they might be OK for you, too.