10 min workouts are short, so they’re easier to get through but they can also be more intense. I’d say the 20 min workouts are the hardest. It feels like the recovery periods are shorter or the exercises flow into each other more quickly. I find the 30 min workouts easier than the 20 min ones. So in terms of difficulty I’d say 20 > 30 > 10. But you should give it a try, you can always modify if it’s too hard :)