The configurator does allow the addition of DHP alone or in conjuction with SAP or M-Sport. The only way to get DDC is through DHP.
I didn't add DHP to my car, so I don't have DDC or any active suspension.
You're correct, the 'tightening up' in sport mode with only SAP and no DHP is just steering. Just double checked this with my BMW sales rep.
You're correct, the Driving Experience Switch will change the suspension with DHP when configured in the iDrive. But I want to emphasize that the key feature of Dynamic Damping Control is not the Driving Experience switch but what goes on behind the scene with the electronic sensors at the wheels.