I have two wordpress sites, one with Rocket, the other with Breeze. On the first site I tried four other popular caching plugins before trying Rocket.
In my experience, Rocket just demolishes everything else, in terms of performance, features, interface, and support. It’s a very, very advanced product.
I’m keeping Breeze on site #2 because performance isn’t as important, and so I’m interested in a free and well-supported plugin.
My server (which runs both sites) is a single-cpu Vultr server. No problems with server load during page preloads. But I set thepreload interval a bit lower than the max, and also have the heartbeat set to reduce theload. I have other plugins that tax the server much more.