Fill a 4-quart stockpot half full with water, add 2 tablespoons of the salt and the potatoes, cover, and bring to a boil over high heat. Cook until just fork-tender but cooked through, 6 to 7 minutes.

While the potatoes cook, mix the mayonnaise, sour cream, scallions, parsley, tarragon, anchovies (if desired), vinegar, lime juice, remaining 1 teaspoon salt, and the black pepper together in a large bowl.

Drain the potatoes well and add them to the bowl; toss with the dressing. Season to taste with salt and black pepper. Let stand for 15 minutes at room temperature (as the salad loses its heat, it will absorb the dressing). Serve at room temperature, or cover and refrigerate for up to 2 days before serving.