Apple Watch comes in four sizes:
40mm (Series 4)
44mm (Series 4)
38mm (Series 3 and earlier)
42mm (Series 3 and earlier)
Show the same content, regardless of display size. Use relative sizing and Dynamic Type to ensure that items expand or contract naturally to fill the available space.
Use one image for all display sizes. Multiple versions of a single image require more space. If an image looks sharp on all display sizes, use it. Use separate images only when a single image does not work. Alternatively, you can also provide a PDF image that automatically scales based on the screen size. For more information, see Provide Autoscaling PDF Images.