On the Windows 10 on Azure front, all users who want access will need to be running Windows 10 Enterprise. Users also will need to be on Windows 10 Current Branch for Business to take advantage of the new option.
Update: Or maybe not. I'm hearing there might be a new Software Assurance Benefit that has nothing to do with License Mobility that will apply to allow users to move their existing Windows Server licenses to Azure.
"You can procure an Azure virtual machine without Windows Server and upload your own customized virtual machine image, including your own installed Windows Server license, to run on Azure," explains Microsoft in an "Azure for Microsoft Software FAQ page.