The adaptive suspension is an option. You can look up your car on
www.mdecoder.com to see if you have it. If so it depends on the configuration of the sport mode setup. It can be configured to be chassis only, power train only or both combined. In chassis only and combined the dampers act differently whether you are in sports mode or not. If you don't have the adaptive suspension there will be no change when entering sports mode.
Here in Europe there is also the option to get the standard suspension as a free option when the M Sport model is chosen. So here you can have the soft suspension in a M sport model. Maybe you have the same option. The M Sport I tried was about the same harshness as my wifes M240i. Which caused me to avoid it.