I don't know how much better Juniper's stuff is, let alone Cloudflare's specific setup, but classic Cisco IOS gear's approach to batching, pretesting and merging configuration changes on mission-critical network infrastructure is basically "f*ck it, we'll do it live on the command line". Real '80s stuff, not far removed from "classic" Unix man-with-a-beard-and-a-Telnet-session configuration management (though the command line largely keeps outright syntax errors out of the config, and the (Nearly) One Big Config File makes basic restore-from-backup relatively straightforward.