The free version of Autoptimize has full features to optimize your WordPress site.
Autooptimize is just an optimization plugin and does not do any caching of HTML pages. This means it’s compatible with all web hosts – even those with custom page caching configurations like Acehweb using Cloud Hosting.
Autoptimize has more than 1 million active installations in the WordPress repository and is consistently updated with new features and bug fixes.
Optimize JS, CSS, and HTML Settings
Optimization CSS via Critital Path CSS Generator