I’m on their free tier. If you don’t have a domain you need to get one, but CloudFlare does offer domain registration basically at-cost.
Because I’m on free, I can’t break down my analytics like a paid account can. i can say though that for the past 30 days my account has generated 886k requests and 47.56GB of bandwidth. I can’t tell you how much of that is nextcloud and how much is other stuff, like audiobookshelf, but hopefully this helps answer you.