I havn't used cloudflare for a couple of years, but it works as a caching server for your whole website. You change your DNS to their servers, and their servers points to your website. Caching data/content as it goes along.
It isn't used in the generation of your pages like VBOptimise optimises. The caching modules the VBOptimise uses are to speed up the page generation.
So Cloudflare is more of a top level caching server, optimises images and gzips JS and CSS and HTML. Can be great for guest caching, however won't help much with logged in users as content is always changing apart from it would work great for the CSS and JS etc.. So worth configuring and giving it ago.
