夢が一番変は何ですか？ is this a proper usage of ichiban? or is it clunky?
I'd probably do something like 何が一番変な夢ですか？ or 一番変な夢は何ですか？ (probably this one).
Your word order is wrong. I'm not good at explaining grammar rules though :(
Edit: Alright, let me try to explain it: 夢が cannot function as the subject here. It's a bit like it's just detached without a valid predicate. 変は has very limited use cases and this isn't one of them. You pretty much need this structure 一番変な夢.
夢が一番変は何ですか？ is this a proper usage of ichiban? or is it clunky?
It kind of feels like 'Dream is the most strange, what is it?" 😅 一番変な夢は何ですか？ is the best as @ギョルギ九十三 suggested. The reason is 変 is a な-adjective and need な when modifying nouns. And you can't use が and は in the same sentence when they are both modifying only one noun. Like : 彼が学生はです => It's because both are competing to mark the same thing. But you can use は + が in the same sentence.
