Carole Ann is an expert on cording! She showed Dori in cords and did all kinds of things with him. She's the one to ask.
I think that if you keep the cords shaped and not one big shapeless mess they'd be easier on both you and the dog. One lady I met told me her dog didnt want to go out much in summer cause the cords were heavy and she'd get hot. She was in long cords all over.
When I cut off all of Dori's cords ( many over 30 cm long) I weighed him before and after removing the coat and there was a grand total of 7 ounces difference. That is it, less than half a pound. So no, they are not heavy, unless soaked with water of course, then he couldn't even hold his tail up, but I did not swim him. it took a long long time to soak his coat with water though. Shorter cords are the way you see them in the US, especially in the show ring, and they would not get weighed down as much with water.
In agility, his tail kept knocking down the bar on the jumps, but his tail cords reached to the ground when he was standing in a normal pose.
A matted coat does not protect against the heat and cold as much as a fluffy coat, since the trapped air is what helps to control the temperature right at the body, but the Marmemma ( spelling is not exact, I don't think) and Komodor etc I understand stay outside all the time as working dogs in cords but they are not black ( although Marmemmma are dark coloured) but their cording is designed to protect them from predators and barbs on bushes etc.
If ( when ) I learn how to add pictures, I will attach some
Carole Ann Brown