Peel and cube the potatoes into 3/4-inch pieces. Place in a large pot, cover with cold water, and add 1/8 teaspoon salt.

Bring to a boil, reduce to a gentle simmer, and cook the potatoes for 8–12 minutes until fork-tender but still firm.

Drain potatoes thoroughly and spread on a large plate or baking sheet until completely cool.

Boil diced carrots for 5–7 minutes. Add peas for the final 2 minutes. Drain, rinse briefly under cold water, and drain thoroughly.

If using eggs, simmer for 10–12 minutes, cool in ice water, peel, and chop. Prepare celery, red onion, green onions, and parsley.

Whisk mayonnaise, sour cream, Dijon mustard, lemon juice, apple cider vinegar, honey, garlic powder, onion powder, salt, black pepper, and paprika until smooth.

Combine cooled potatoes, carrots, peas, celery, red onion, and green onions in a large bowl. Gently add chopped eggs if using.

Pour dressing over vegetables and fold gently until coated. Add chopped parsley and gently combine.

Cover and refrigerate for at least 1 hour to blend flavors and thicken the dressing.

Stir gently, transfer to a serving bowl, garnish with additional parsley, green onions, and paprika if desired, and serve chilled.