Cook the pasta: Boil in well-salted water until just al dente.
Drain and rinse under cool water to stop cooking. Shake off excess water.
Cook the bacon: While pasta cooks, crisp the bacon in a skillet or bake in the oven. Drain on paper towels, then crumble.
Prep the veggies: Halve the tomatoes, chop the cucumber, and finely dice the red onion.
If using corn, thaw or drain it.
Make the dressing: In a bowl, whisk ranch dressing, sour cream (or yogurt), lemon juice, garlic powder, and black pepper. Taste and adjust salt if needed.
Toss the base: In a large bowl, combine cooled pasta, tomatoes, cucumber, onion, and corn. Add the cheddar and herbs.
Add dressing: Pour in about 3/4 of the dressing.
Toss gently to coat. Add more if needed for a creamy but not soupy salad.
Fold in bacon: Add most of the crumbled bacon, reserving a little for garnish. Toss lightly.
Chill: Cover and refrigerate at least 30–60 minutes to let the flavors meld.
The pasta will absorb some dressing as it rests.
Finish and serve: Before serving, taste and add a splash more dressing or a squeeze of lemon if it’s tightened up. Top with remaining bacon and extra herbs. Serve cold.