Scrub and rinse unpeeled potatoes, then cut them into 1-inch cubes.
Place potatoes in a large pot of salted water, with just enough water to cover them.
Bring to a boil over high heat, then reduce to a gentle boil and cook the potatoes for 7-8 minutes (or until they are fork-tender).
Drain and rinse the potatoes, then place them in the refrigerator to cool for 30 minutes.
Meanwhile, in a large bowl (big enough to hold the potatoes), whisk the sour cream, mayonnaise, vinegar, 2 teaspoons salt & 1 teaspoon pepper until smooth.
When the potatoes are cooled, gently fold them into the dressing until coated.
Fold in 1 cup of cheese, half of the bacon, and half of the green onions. Season with more salt to taste, if desired.
Chill for at least 30 minutes, and up to 2 hours.
Garnish with the remaining cheese, bacon, and green onions, and serve.