1) https://www.webpagetest.org for analyzing loading times
2) a3 lazy load for lazy-loading images: https://wordpress.org/plugins/a3-lazy-load/
3) autoptimize for combining multiple CSS files: https://wordpress.org/plugins/autoptimize/
More description of what we did at my write-up here: https://hackernoon.com/dont-brake-for-fonts-3-web-performanc...
In my experience the biggest issue with with slow load times are people uploading large unoptimized images. Things like multiple css/js files, unnessary plugins and framework are nothing compared to people using uncompressed large images. Use a plugin, ImageOptim or cloudinary.
It loads the page and the text first so you can start reading. The images and scripts are delayed and cached. Comments are last. Pictures and thumbnails have various resolutions to improve load time.
Most i've seen load 5+ CSS files and least 10+ JS.
So how does this product helps in this case?