Was you an Windows 10 insider? Yes I was - but not really active
This looks easier than downloading an ISO. - Sure it is!
Did it restore to 8.1 first and then update to 10? - NO - if you choose to go that way i.e. a complete restore, you loose your 8.1 copy. The side benefit of this is that after the restore, you have much more free disk space left!
I'm thinking of doing this as someone was using my Surface pro3 and decided to install some bits and now it runs hot with the fan constantly going.
As I didn't set up system restore I can't seem to go back