it has something to do with file vault encryption, you can either restart and not choose a wifi during setup or wait about 30-40 mins to see if it resolves the issue by itself.
Yes to both. 😉 Remember that FV won't run on battery power (so, for example, if you leave the computer running overnight, but unplugged, FV won't continue encryption).
The best way to set it up is by not connecting to the internet during the main pages. It literally took me 10-20 seconds to be on the home screen. After that, I set up file vault and my iCloud account without problem.