Looking at the home screens, the primary difference you'll find is that in iOS 26 the background of the dock and the search option that sits in between the dock and the home screen icons are more transparent and have a sheen to the edges, whereas in iOS 18, these are slightly darker.

Apple apparently wasn’t satisfied with the Liquid Glass look in beta 2. iOS 26 beta 3 introduces another change, and now the glass isn’t that liquid anymore. The transparency has been reduced even further, giving the overall effect of frosted glass.

Apple's streaming music app's navigation bar now has a more solid white background. Notifications are also slightly translucent because of the increased contrast caused by the darker background behind the text.