'delicate', yes I think it's absolutely tied to 'impractical' in my mind. 'elegant' maybe isn't the right word for what Im' feeling here. As an engineer, I see elegance in practicality, efficiency, and straightforwardness.
'artistic' or 'aesthetic', maybe, for the second one?
Like you, I tend to see efficiency as most beautiful, especially when one simple structure fulfills several complex requirements simultaneously. A tiger or a gazelle is beautiful because it's very close to optimal for the niche it's evolved to fill.
I dunno but maybe it's the equivalent of countershading camouflage? Tigers are ambush predators that attack from above. If a tiger's fur only accounts for a small percentage of the sky above you, and orange and blue are complementary colours, then small bits of orange fur plus blue sky shouldn't stand out.
