There's an easy way to tell whether or not you'll see a benefit from CF performance. Turn it on / off for your site temporarily, then watch the load times.
CF does indeed help your site load time and performance in a number of ways
#1: Caching (if enabled) will speed up your response time
#2: DNS hosted at CF means less work on your server. Fewer requests = better performance
#3: CDN means your site loads static objects from a location closer to the end user than your server
#4: Threat protection. Again, anything taken away from the server is good.
If you're not seeing a performance increase with CF, even on a free account, then you've probably not got it configured properly. There is absolutely
a definite performance increase