Who can see my profile and what exactly is it they see?

Your profile is public. Anyone with the link, or anyone who clicks through after reading one of your reviews, can see it. Visitors can view your ratings, reviews, Favorites, and any custom lists you've created, but not your Watchlist, which stays private and is only visible on your Films page. Use the Public Profile menu at the top right of your profile and select View as guest to see exactly what visitors see.

Your Watchlist doesn't appear on your profile. Your Watchlist contains all the movies you want to watch and is located on your Films page.