Gonzales gpl allows to conditionally load CSS, JS and even plugins depending on page you visit. It’s simple and lightweight tool thanks which you’ll be able to get rid of useless CSS and JS files registered by themes and plugins.
Just be clear, this WordPress plugin do not remove files from server – it’s safe speeding up tool. If you accidentally break website appearance you can disable plugin and website will present old, unoptimized version. Btw: it’s good approach to compare before/after timings 🙂