For what it’s worth, in the German, Schopenauer wrote: “Ein Mensch kann zwar tun, was er will, aber nicht wollen, was er will.” My non-expert literal translation is: A person can indeed do what he wants, but not want as he wants. In German, wollen is the infinitive of the verb to want, while tun is the infinitive of to do (an alternative of machen, or to make). Query: How do you interpret Schopenhauer’s comment in the context of his work, The World as Will and Representation? (Die Welt als Wille und Vorstellung”?)
For us anglophones, to will is to want something rather explicitly in conscious terms. To want may alternatively have to do with underlying tastes and preferences beyond conscious control. I take issue with your English translation, though native German speakers may have something more insightful to say about this.
If we are looking for “true” interpretations, that is, interpretations mostly likely to have been intended by Schopenhauer, then I would count your third interpetation as being the closest. None of them actually reflect what he is literally saying. I believe, from what I remember barely of Schopenhauer, he viewed ultimate reality as a pervasive underlying Will, a thing in itself (das Ding an Sich) which did not even know what it wanted.
Schopenhauer could not have intended as true more modern interpetations relying upon modern facts about the world, such as cognitive systems, because such facts were not accessible to him writing as he did in the 19th century.