01 - Boil pasta in generously salted water until al dente, following package directions. Drain in a colander and rinse immediately under cold running water to halt cooking. Spread on a sheet pan or transfer to a large bowl to cool completely.
02 - In a large mixing bowl, whisk together mayonnaise, sour cream, and ranch seasoning packet until smooth and well combined. Stir in 1 tablespoon of milk, adding a second if needed, to reach a pourable but still creamy consistency.
03 - Add the cooled pasta to the dressing and toss thoroughly until every piece is evenly coated.
04 - Gently fold in the halved cherry tomatoes, diced bell pepper, shredded cheddar, bacon bits, sliced green onions, and thawed peas, being careful not to crush the tomatoes.
05 - Taste the salad and adjust salt, pepper, or an extra splash of milk as needed. Mix until all ingredients are evenly distributed throughout.
06 - Cover and refrigerate for at least 30 minutes to allow the flavors to meld and the dressing to fully absorb into the pasta. Serve cold.