Yes, the new Sun and Sky simulates the visual effects of a sun and a planet’s atmosphere. When Sun and Sky is used as a lightdome, the global light acts as the sun.
Sun and Sky offers a lot of possibilities in setting intensity. You can adjust the lightdome intensity, the global light intensity, the intensity of the atmosphere in the Sun and Sky dialog, and also the intensity of the light in the Sun and Sky dialog independent of the other values.
It is not recommended that you rotate the lightdome once you have this set up, instead just move the global light around. Otherwise it'll get confusing.
As an example of the possibilities of Sun and Sky, you can leave the global light at 95% (default) intensity, but then set that intensity to zero in the Sun and Sky dialog.
This will keep the atmosphere 'lit' but not provide direct illumination. This is useful if you want to use a spot light instead of the global light for situations where you want soft shadows, something a global light can't provide.
If you do do this then you'll need to manually match the coloration the global light would receive from passing through the atmosphere, especially if it's low to the horizon. The global light needs to be above the horizon.