vmr providers are “tools” that manage the virtual machines instances such as VirtualBox (default in vmr), docker, vmware, aws, openstack, …
Actually only VirtualBox is available in vmr package.
vmr can manage some of virtualbox options.
Options available can be find here:
To set a name to the virtualbox machine:
To disable GUI:
To add more cpus and memory:
More options can be find here https://www.virtualbox.org/manual/ch08.html#vboxmanage-modifyvm