Before starting, apply this settings by default for your Sketch documents. Use the grid for spacing management and for designing new components. The grid is your best friend for creating mockups on full screen applications, the layouts should be used for designing websites or mobile apps.
The layouts are mainly used for designing websites with a container. For full screen applications please use the grid system instead.
You can find detailed explanations to configure your Sketch files in the "Get Started" page inside the UI Kit.