Place potatoes in a medium saucepan and cover with cold water. Heat to boiling over high heat, add 2 tablespoons kosher salt, then reduce heat to medium and cook 15 minutes or until fork-tender but not falling apart, stirring occasionally.

Drain potatoes (do not rinse), then transfer to large bowl and let cool 5 minutes. 

Meanwhile, in medium bowl, whisk mayonnaise, sour cream, mustard, vinegar, sugar, pepper, paprika and remaining 1 teaspoon salt until smooth. Place half of dressing in small covered bowl and refrigerate until ready to serve salad.

Add remaining half of mayonnaise mixture to bowl with potatoes and toss until well combined. Cover and refrigerate at least 2 hours or up to overnight. 

Just before serving, add bacon, onion and reserved dressing to potatoes and toss until well combined.