If you have never done a clean install before then maybe the first option will be easiest for you. So you understand this will delete everything, all your files, all your programs, drivers and you will be back at the start with nothing. You will need re-install everything and remember to back up everything you want to keep, so it can be moved back onto your clean install.
From what I'm reading now, I see when you go to 'reset my pc' you will be given the option to backup your files, though I would still prefer to back them up myself just to be certain, especially if you have very important data you need to keep. Also if you do this you won't be able to undo the upgrade and go back to your previous windows.