If you are familiar with Harden's game at all, you will realize that Howard is a perfect partner for him. He either shoots a three, drives in for a layup (and attempting to get an and-1 every single time) or dishes out/in while he drives in. All Dwight has to do is catch and dunk, or rebound and dunk. There is no post game necessary.
I'm not as optimistic about Smith however. The past few years he has developed some bizzare idea that he is a 3-pt shooter, and consistently passes up opportunities to score in the paint, where he excels, for bad shots in the corner. In a way, I suppose that would be good for Howard and Harden to open up the floor, but if I were Mchale and co. I'd want to utilize his talents that you're paying a max contract for.