のやら～のやら

のやら～のやら sets two possibilities side by side and says you can't tell which is true: "whether … or …, who knows". Each half ends in the plain form before のやら, and a な-adjective or a noun takes な first.

• × 本当のやら嘘のやら → 本当なのやら嘘なのやら

The two halves are usually opposites, or two things that pull different ways. The sentence goes on to say you can't tell – わからない分からない, はんだん判断がつかない – or describes the state you are in.

のやら～のやら or やら～やら

Without の, やらから～やら lists things that are all true, usually with a complaint about the pile-up. のやら～のやら offers alternatives and can't decide between them. With feelings the gap is small: 嬉しいやら恥ずかしいやら is feeling both at once, and 嬉しいのやら恥ずかしいのやら is not knowing which.

• × 本のやら雑誌のやらが散らばっていた → 本やら雑誌やらが散らばっていた

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The pattern is written, or deliberate in speech: narration, essays, a speaker describing their own confusion. In conversation のか〜～のか says the same plainly.