Bring a pot of water to a boil, then cook the russet potatoes at a steady boil for 15-20 minutes, until a fork slides in easily. Drain and cool completely until no steam remains.

Chop the hard-boiled eggs and set them aside for mixing. Keep them at room temperature only briefly so the potatoes can finish cooling.

Combine the cooled russet potatoes, hard-boiled eggs, celery, onion, and sweet pickle relish in a large bowl and fold to distribute evenly. The mixture should look studded with egg and relish pieces.

Stir mayonnaise, yellow mustard, white vinegar, sugar, salt, and pepper together until smooth. Taste once and adjust seasoning with a pinch of salt or pepper as needed.

Pour the dressing over the potato mixture and fold gently until every cube is coated. Stop folding when the salad looks creamy and cohesive, not mashed.

Cover and refrigerate for at least 2 hours to let flavors blend and thicken slightly. You should see a more cohesive, creamy texture after chilling.

Right before serving, garnish the top with paprika for a classic presentation. Serve cold, with extra paprika optional.