Could you please open an issue on GitHub for both of these issues. We can improve the documentation for the config options and make sure that the fields.yml is correct. It would really help if you could call out the fields that are different/missing.
From researching the `get_custom_fields` I believe that setting this to true causes the virtualmachine metricset to report all of the [custom attributes](https://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.vcenterhost.doc%2FGUID-25244732-D473-4857-A471-579257B6D95F.html
) set on the virtual machine. Hopefully after opening the GH issue we can get confirmation from the original [author](https://github.com/elastic/beats/pull/4469
) of the module. We might also want to consider renaming the config option to `virtualmachine.include_custom_attributes` to help clarify what metricset it affects and what it does.