Icecap: the minimum temperatures quoted are for cold spells or storms in the spring and autumn. Much of the time it can be warmer than this, even more so in the summer. The cold weather is usually accompanied by high winds, making windchill a serious factor.
Coast: For climbing/kayaking near the coast, the summer minimum is likely to be 0°C in the day, -10/-15°C at night.
Wind chill rating: High
Travel in Greenland includes ski (+ sled), kiting, and dogsledding, for journeys of all lengths right up to 2500km and with varying degrees of support (if any). Weight is very important for self-powered expeditions, a little less critical for kiters and dogsledders.
The humidity on the icecap is quite low - more like Antarctica, so VBLs are not the necessity that they are for the North Pole. Extra length is advised on bags for storing vital items at night.