Place potatoes in a large pot and cover with water. Bring to a boil and cook until potatoes are tender, about 15-20 minutes. Drain and let cool slightly.
While still warm, cut the potatoes into bite-sized pieces and place in a large bowl. Sprinkle with vinegar and a pinch of salt.
In a separate bowl, mix together sour cream, mayonnaise, and mustard. Add this dressing to the potatoes and gently mix.
Add the chopped red onion, celery, dill pickle, and optional hard-boiled eggs to the bowl with potatoes. Stir to combine.