A couple of new features that I noticed is the ability to double-tap the screen to wake up the display and the addition of Digital Wellbeing. Additionally, I think there may also be some minor UI improvements in areas.
One UI 1.0 is also likely coming to the Galaxy Watch soon and it adds a couple of really nice, if quite small, features(e.g. tap to wake, pages for quick settings so that you can have more than eight, and colors in the settings that match up with One UI on Android.
Sorry, I have no idea. But, I am praying they bring back the ability to easily enable Single Tap to Swipe. This is a complete disaster in One UI 1.0.