It's not missing anything from the base model - 10 speaker audio, electric tailgate, Lexus Link Pro are all Premium Pack Plus items.
F Sport Design is essentially a UX with a Premium Pack and the 18" wheels, Tahara, BSM and RCTA options with some F Sport styling but in a special edition way nothing is configurable so you cannot upgrade to the 10 speaker stereo, leather, etc. The only choice you have is interior and exterior colour.