Bring a large pot of water to a boil over high heat, then add the peeled and cubed potatoes and cook until tender, about 15–20 minutes. You should be able to pierce a cube easily with a fork.

Drain the potatoes and spread them out to cool for 5–10 minutes. The surface should look dry and the cubes should no longer steam.

Stir together mayonnaise, sour cream, white vinegar, sugar, salt, and pepper until smooth. The dressing should look thick and glossy.

In a large bowl, combine the cooled potatoes with the cooked and crumbled bacon, diced celery, and sliced green onions. Toss gently until the mix-ins are evenly distributed.

Pour the dressing over the potato mixture and toss well to coat every cube. Keep tossing until the salad looks creamy and well bound.

Refrigerate the potato salad for 2 hours before serving, covered. Chill until cold throughout and slightly thicker in texture.