Otimize HTML Code? : Enable
Enable : Keep HTML comments? Enable this if you want HTML comments to remain in the page, needed for e.g. AdSense to function properly.
Optimize CSS Code? :Enable
Disable : Generate data: URIs for images? Enable this to include small background-images in the CSS itself instead of as separate downloads.
Still some issues are there in Autoptimize 1.9 , in the upcoming versions you will see the complete control on inline and defer CSS. You need to enter optimized CSS code manually in advanced options of Autoptimize settings to completely eliminates render-blocking CSS in above-the-fold content.
Async JS and CSS plugin is the best alternative to this Auto optimize WordPress plugin. It was not updated for the past couple of years, even though, it's working perfectly.