Thanks for your posting and please see below for my answers:
Yes, VMware or other virtualization technologies are fully supported and many customers use TestRail on a virtual server with Windows or Linux/Unix as guest operating system. For larger TestRail installations, we recommend taking care that the virtual server has a reasonable strong I/O system (as this is usually the bottleneck with virtual servers).
The SQL Server doesn’t have to be on the same server as TestRail and you can connect to an external server as well. You can configure the SQL connection (address, user name, password, etc.) during the installation wizard as the first step.
LDAP/AD integration is fully supported with self-hosted installations and you can configure the integration as follows:
I hope this helps and please let me know in case you have any additional questions about any of these points.