Place the potatoes in a large pan and fill with cold water. Add 2 tablespoons salt and bring to a boil. Reduce heat and simmer until the potatoes are tender, about 15 minutes.
Drain and return the potatoes to the hot pot. Add the olive oil, vinegar, 1 teaspoon salt, and ½ teaspoon pepper, and stir to coat the potatoes well. Let sit at room temperature to cool.
Once the potatoes have cooled, transfer to a large mixing bowl. Add the mayonnaise, sour cream, green onions, celery, and chives, and stir well. Taste and add more salt and pepper, if needed. Cover and refrigerate until cold, at least 4 hours. Can be made 1-2 days ahead.