When I updated to win 7, they made the online package available for a number of years..To back myself up, I saved a copy of it.
I don’t know how they will do this one. If I recall the win 8 beta was a similar setup..
I have not yet received my win 10 update so I am reluctant to guess what the procedure is.
Believe you can burn an ISO image from a download of win 10.
Go to Microsoft site and check all the possible solutions.
Yes, you’ll be able to get an .iso which you can save to USB or optical.
Search on clean install Windows 10 or Windows 10 iso or similar terms.