How to get intended taste using baking powder instead of acid + baking soda?
If you use baking powder instead of baking soda in this recipe, you'll have an excess of acid.  That's not too bad (an excess of baking soda gives a soapy, bitter flavour).  The effect is likely to be as if your sour cream was slightly more sour. If you wish to tone that effect down you could  replace a small amount of your sour cream with cream or even milk.

The rise may be slightly affected but this should be minor; with or without the acid in the baking powder you're limited by the alkaline component. Baking powder is usally double-acting meaning some of the reaction is delayed until it gets hot. Sour cream plus baking soda is likely to start reacting immediately, so substituting the other way would be worse.