Preheat the oven: Set to 375°F (190°C).
Lightly oil a 9x13-inch baking dish.
Cook the shells: Boil in salted water until just shy of al dente. Drain and rinse under cool water so they’re easier to handle. Pat dry.
Mix the filling: In a large bowl, stir together cream cheese, ranch, half the BBQ sauce (1/2 cup), garlic, smoked paprika, salt, and pepper until smooth.
Add chicken and onions: Fold in shredded chicken, half the shredded cheese, and most of the green onions.
Taste and adjust seasonings.
Sauce the dish: Spread the remaining 1/2 cup BBQ sauce over the bottom of the baking dish.
Stuff the shells: Fill each shell with about 2 tablespoons of the chicken mixture and nestle them into the sauced dish, open side up.
Top with cheese: Sprinkle the remaining shredded cheese over the shells.
Bake: Cover loosely with foil and bake for 15 minutes. Remove foil and bake another 10–12 minutes, until the cheese is melted and bubbly with light golden spots.
Finish and serve: Let rest 5 minutes. Garnish with remaining green onions and chopped cilantro or parsley.
Serve warm.