Personally, I think a lot of those workouts utilize both. I feel, as long as your huffing and puffing, you’re getting your heart rate up and you are effectively doing cardio.
If you do strength training in circuits, you will get the best of both worlds.
I’ve been sticking with varieties of push ups, pull ups, lunges, split squats, regular squats. Mostly bodyweight exercises with added weight, or somehow making them more difficult.
The workouts at those links I posted are pretty intense. A mainstay is the classic burpee which is good conditioning and cardio combined.
I would say the idea is to get strong and build endurance.
Hope that helps. I haven’t actually done the particular routines on those sites, but I’ve taken a few of their ideas and tried to use them.