What are the system requirements like RAM & cores etc. If we use the departmental architecture in Virtual machine.
If you're wanting to know how to deploy Splunk in a Virtual Environment, you should read this first : https://www.splunk.com/pdfs/technical-briefs/splunk-deploying-vmware-tech-brief.pdf
Thats a good starting point. And from what you are calling a departmental architecture, this could be a standalone or distributed environment depending on your use cases and daily volumes of indexing.
Best practice is to not deploy Splunk infrastructure as a VM, regardless of settings.