Olivier responded about ARN. As for landside CPH security you can use fast track if you are in business/plus (or are EBG). Otherwise you need to go with everybody. But even there I have never seen this being over 20 minutes.

In my experience the bottle neck in CPH is rather the checkin, especially if it happens that several cruise ships terminate on that day in the town. It is a bit unpredictable. Summer Sunday can be busy, but I think the biggest traffic is earlier in the month. Also around 3pm when you will be arrivign at the airport, the wave of long hauls is already processed. In any case be prepared to use business check in if you have bags, or better travel without hold luggage if you want to save time or maximize your luck.