Visited Emerald Lake in early September and did the whole loop clockwise. It turned out to be approx 5.5 km total and was a very easy and pleasant walk. Majority of the trail is an even path, with just some forest parts requiring to walk on a wooden boardwalk. Regardless of the insane crowds at the parking lot and around the chalets, the path actually gets quite quiet and not so crowded as you move towards the other side of the lake.
Check out the nice beach at the other side of the lake (from the chalet) – nice views. The little gift shop at the main chalet has a great selection of quality products as well as rents kayaks and canoes. Washrooms available right next to the chalets. Great place and a nice trail for any level of fitness and regardless of the weather.