Your estimate the of the QVW size in RAM seems very high to me. The best method is to actually open the QVW and see how much the RAM jumps up and use that number. Your per concurrent users number is conservative. Typically a range of 8-10% is used.
As to the the OS and the QV Server this will be so much smaller than the RAM used the by QVWs that I wouldn't worry about it. Just round up from what you estimate by the QVWs.
The type of license will make not impact on the resource requirements.
Finally you can get a much more accurate understanding of the resources requirements by looking at your current environment. I would recommend download the Ops Monitor or Governance Dashboard. They will pull all your log files together and show you your real world usage vs uses these estimates.
If we have 40 concurrent users. How much CPU power would you recommend. I understand that it all depends on usage and what QVW those users are accessing. However lets assume we have 6gb worth of QVW and all of them are being access by 40 concurrent users. I am able to determine RAM size however not sure how to go about determining # of CPU & Cores required. What are basic formula.