asked this a while back: で as 動作を行うときの様態 vs で as だ. But i don't feel this aspect has ever become intuitive at all, especially for adjectives.
eg.
爽やかで抜けるような青空と、この香りとは対照的に、大きくせり出した柵のグレーが強い拒絶を示している。
(speaker in a prison by the ocean) The gray of the large jutting fence shows a strong rejection in contrast to the "爽やかで抜けるような(invigorating, like it was escaping)" sky and ocean scent.
結果は今ひとつでナンパにも技術が必要だと身にしみた
In the end I have come to realize "今ひとつで(i am lacking?)", even nanpa requires considerable skill.
i lean towards で as だ for both of these, but it's an very disjunctive read and very hard to naturally translate.
When does someone purposely choose to use this sort of sentence structure?