I spent 3 days on Orchid Island last October and thought it was great. Not crowded, slow pace, beautiful natural coastal scenery, goats everywhere in the hills…
My buddy and I did a tour of an old style local underground home, which was conducted by an older resident (the home belongs to her family). It was an intimate and very interesting look at the old way of life there.
Definitely rent a scooter and ride all around the island. My friend and I rented some snorkel equipment and went to the spot the shop recommended, right by that Taiwan Power place. It was a beautiful spot to see the undersea life (no seven-eyed fish or anything) and there was only a couple of other people there…not a big group all strung together with their life jackets.
We were lucky enough to be there when a fishing boat race was being held in the north part of the island. However, we witnessed a terrible tragedy so we didn’t stay for much of the race. Anyway, I highly recommend Lanyu. Try the barbecued goat and flying fish