With the release of iOS11, it has introduced many new UI components and layout. Due to the different screen dimension of iPhone X, there will be a significant update to the UI kits.
Here we have a free and massive collection of core components and over 60 (x2) selected screens found in the public release of iOS 11. It's created by iOS Design Kit. You will get UI design for both iPhone X and iPhone 8 in Sketch format.