Mix sour cream, salsa verde, and cilantro together in a bowl until sauce is evenly mixed; refrigerate.
Place potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 10 minutes. Drain and cool in a large bowl.
Set oven rack about 6 inches from the heat source and preheat the oven's broiler. Line a baking sheet with aluminum foil and place peppers on the baking sheet.
Cook under the preheated broiler until the skin of the peppers has blackened and blistered, 3 to 4 minutes. Place blackened peppers into a bowl and tightly seal with plastic wrap. Allow peppers to steam as they cool, about 20 minutes.
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Reserve 1 tablespoon bacon grease in the skillet. Drain bacon slices on paper towels and chop.
Combine red bell pepper, onion, and garlic in the skillet with reserved bacon grease; cook and stir over medium heat until vegetables are softened, 4 to 6 minutes.
Mix 1/2 of the bacon, red bell pepper mixture, Cheddar cheese, milk, and butter into the potatoes; mash until well blended.
Remove skins from the roasted poblano peppers. Make a small cut in each pepper and scrape out seeds. Stuff peppers with potato mixture and top with remaining bacon and sauce.