The Nougat update to the Galaxy S7 and S7 edge introduces a new display scaling option that lets you reduce the screen resolution as a way to conserve battery life. With the update, you can now choose between three modes — WQHD (2560x1440), FHD (1920x1080), and HD (1280x720). While it's a nifty feature to have, the display on the Galaxy S7 and S7 edge is automatically defaulting to Full HD for those that have installed the update.
The display on the S7 and S7 edge looks great even on Full HD, and for the most part, there isn't a lot of difference when viewing text and images in Full HD when compared to QHD. As we've seen when the feature first rolled out during the Nougat beta test, it is likely Samsung is defaulting the screen to Full HD to extend battery life and improve performance. Fortunately, you can easily switch back to the native Quad HD resolution by navigating to Settings -> Display.