Docker vs CMS - related or a different thing?
Something like puppet would help automate and configure the Docker Container.  CMS is configuration/provisioning and Docker is like you said a virtualization platform.  You're trying to compare two completely different things.  Here is an article on how to configure puppet with docker, sometimes an example helps.  https://puppet.com/blog/building-docker-images-puppet

For another way to classify, Docker is the VM you host your software.  CMS is automation on how to provision it. 

As a side note, most people are moving to Kubernetes to orchestrate and provision containers on the cloud.