很高兴为你解答.
由于你只说了分析画线的what 的成分,不知道你说的哪个：
So if what they had said was true , I would have a chance of winning the prize
如果他们说的都是真的话,我就有赢得奖项的机会.
what 在这里引导主语从句,做主语从句中said的宾语.
what they had said 是条件状语从句中的主语,was 是系动词,true 是表语.
What was better , I had useful help
更好的是,我得到了有益的帮助.
这里 What was better 是作插入语,和 what's worse,what's more 这种有点类似.它不是指具体的什么东西,就像我们说的Everything is possible 一样,what 是当作一个整体,用单数形式.
望采纳,祝开心~!