According to Android Police, one of the changes will let you know whether people on your Duo contacts list are avid users of the app. When scrolling through this list, you'll see the words "on Duo often" next to those contacts who, well, use Duo often. This will help you figure out which of your Duo contacts is more apt to answer your video call or respond to a video message.
The second change can be found on the Contact Screen where you'll see a new box near the bottom of the display that says "Calling as..." with your phone number listed. This is supposed to remind you that those you are engaging in a video chat with or sending a video message to can see your phone number. And if you have a dual SIM device, it will also show you which of your two numbers is involved in your Duo call or message.
The third change won't necessarily improve the user experience of the Duo app except to make you feel more secure. This is an addition to the app's menu that adds a link to a new support page called Privacy for calls. This page details how Duo's end-to-end encryption keeps your video and audio conversations private. The page notes that "Only people in a call can know whats said or shown. Google cant see, hear, or save your calls audio and video."