You'll need a license for a clean install on a machine that hasn't run 10 before. I see you know about W10T2 so I won't elaborate.
License discussions are so well done now so I'll just answer the new build needs a license question. Your choice to wait or not.
I am going to upgrade from Win7. Should I wait till Threshold 2 or update right now via GWX? Also, will the Media Creation Tool update itself directly to the new build? What is new in this update apart from UI changes, insiders?