Check your content petcantage by domain using pingdom.
Ex: my domain content petcantage is 24%.
Fonts 16% which is serverd fonts.google.
Google AdSense 30_50% via pagead.google.com
Google analytics 6%>.
Google tagservices 5%
onesignal push notifications :10%.
So cloudflare caches 24%content and it only caches 5-10% request out of 40 requests because those are from third party.
To increase performance you have to enable full page caching with cloudflare pagerules cache everything and cloudflare plugin at WordPress to automatically purge cache while on update.
also I am thinking fastcgi because cloudflare missing requests sometimes (based their budget for free plan).