Peel and cut the potatoes into bite-sized chunks. Boil them in salted water until they are fork-tender but not mushy—about 10 to 12 minutes. Drain and set aside to cool completely.
Peel the boiled eggs, then cut each one in half. Scoop out the yolks and transfer them to a mixing bowl. Mash them with mayonnaise, mustard, vinegar, salt, and pepper until you have a smooth, creamy mixture.
Chop the egg whites and mix them with the cooled potatoes, celery, red onion, and pickles or relish. Add the devilled yolk mixture and gently fold it in until all the ingredients are well coated.
Transfer the salad to a serving dish, sprinkle paprika on top, and garnish with herbs if desired. Cover the bowl and refrigerate for at least one hour before serving.
