substitution of ingredients
Could I use greek yogurt instead of sour cream?
What about buttermilk instead of whole milk?
I wouldn't use buttermilk AND yogurt. I'd thin the Greek yogurt slightly to sub for the sour cream and use reduced fat milk instead of the whole milk.
Yes to both, and no need to alter amounts. I've done this with biscuits, quite similar to the scone dough.
Yes, although I'd use full fat greek yogurt (which is already lower in fat than sour cream) especially if you're using buttermilk, unless you find some that isn't low fat. It would work w/ lower fat greek yogurt but I think it would be much richer.