Place the diced potatoes into a large saucepan and cover them with cold water. Stir in the measured salt and bring the mixture to a boil. Lower the heat to a gentle simmer and cook the potatoes for approximately 12 to 15 minutes, or until just tender when pierced with a fork. Drain well and let them cool slightly.
In a spacious mixing bowl, prepare the dressing by combining mayonnaise, yellow mustard, relish, apple cider vinegar, paprika, black pepper, and a pinch of salt. Whisk thoroughly until smooth and uniform in texture.
Gently incorporate the cooled potatoes, chopped eggs, celery, and onion into the prepared dressing. Use a spatula to fold the mixture together carefully, ensuring the potatoes remain largely intact while fully coated.
If time allows, cover the bowl with plastic wrap and refrigerate for at least an hour to enhance the flavor.
When ready to serve, transfer the salad to a serving dish. Lightly dust with additional paprika and garnish with sliced green onions or chopped pickles if desired.