There is an interesting situation with caching mechanisms such as Cloudflare and many others; where the benefit of caching the website for speed only comes in when you have significant traffic and simultaneous traffic to your website.
Some caching plugins take more server resources initially, and actually tend to slow down your site than speed it up, until the user traffic increases and then you see the benefit of the caching for speed.
As for security aspect of Cloudflare much of the security options are available for free. If you don't realize the benefit of the paid subscription you can still enjoy the security benefits of the free option.
Hope this helps

