Combine couscous, mint, and cilantro in a bowl. Pour in boiling water. Cover and let stand until couscous is soft, about 5 minutes.
Place chicken breasts between 2 sheets of heavy plastic on a solid, level surface; pound firmly with the smooth side of a meat mallet to 1-inch thickness. Season both sides with paprika, salt, and pepper.
Heat a large nonstick skillet over medium heat. Cook chicken breasts until no longer pink in the center and the juices run clear, about 5 minutes per side. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Slice chicken into strips.
Combine green bell pepper and red bell pepper in the same skillet used to cook the chicken; cook and stir over high heat until blackened in spots, about 5 minutes.
Spread couscous over the bottom a large serving plate. Top with chicken slices, pepper mixture, mango, avocado, watercress, feta cheese, and yogurt.