Preheat oven to 400°F. Line a large rimmed baking sheet with foil or parchment paper and set aside.
In a large bowl, combine ground chicken, 3/4 cup Parmesan, 3/4 cup Panko breadcrumbs, eggs, 2 tablespoons Italian seasoning, Worcestershire sauce, garlic salt, onion powder, and pepper. Use your hands to gently mix ingredients until thoroughly combined but not packed down. Scoop meat into 3-tablespoon mounds (I use a 3 T. cookie scoop) and gently roll into balls (which should measure between 1 1/2 and 2 inches across for about 21 meatballs).
In a small bowl, combine 1/4 cup Parmesan cheese and remaining 1/4 cup Panko breadcrumbs. Roll each meatball in the mixture until coated on all sides.
Arrange meatballs on prepared baking sheet, at least an inch apart. Bake meatballs for 15 minutes. Broil for an additional 2 to 3 minutes (watching closely!) until meatballs are golden brown on top with an internal temperature of 165°F. Remove to a paper towel-lined plate to drain any grease.
While meatballs are baking, pour marinara in a large, deep skillet (12- to 14-inch diameter). Season with remaining 1 tablespoon Italian seasoning and a pinch of sugar. Bring to a low simmer over medium heat. Once the meatballs are cooked and drained, carefully place them in the skillet of warm sauce, turning each meatball so that all sides are coated. Sprinkle with mozzarella and remaining 1/4 cup grated Parmesan. Cover skillet until cheese is melted. Serve hot as-is, over pasta, or on sandwich rolls for meatball subs.