VM Manager is three separate services, one of which is "OS config management", which is more akin to Ansible (or Puppet, Chef, etc), i.e. provisioning software on a system. The other two services look after themselves TBH.

The OS config mangement in practice is a daemon that polls for "guest policies" every 10 minutes. Their example policies will give you a good idea of what it does:

https://cloud.google.com/compute/docs/os-config-management/c...

Or better still, the `google_os_config_guest_policies` terraform resource:

https://registry.terraform.io/providers/hashicorp/google/lat...

(Essentially it's pretty basic stuff: configuring package repos, installing packages, running scripts, and copying artefacts).