PageSpeed Autoptimize css query strings

You’re slightly mixing up things here;
* remove query strings -> AO does not add those to the autoptimized JS/ CSS, and upon checking your page source I don’t see those being added (except for one autoptimize_single-file, see below for more info).
* remove unused CSS -> that is something AO cannot do; it simply combines the CSS found in the non-optimized version of the page. If you use complex themes and/ or plugins that add a lot of CSS, then AO will just combine that. If you want less CSS you’ll have to find (or create) a simpler (child-)theme and/ or remove plugins (optionally conditionally with e.g. plugin organizer)
* having multiple autoptimize CSS-files; the default settings exclude CSS-files in wp-content/cache and wp-content/uploads to prevent cache size issues because of frequently changing CSS. These excluded files are minified by AO if not done so already (based on filename). This is the reason for the 3 “autoptimize_single_xzy.css”-files. If you want to avoid that feel free to change the exclusion list (but keep an eye on cache size).

Hope this clarifies,
frank