Short and clear: There is no technical difference in content between "Samsung SWA-9500S/XN" and "Samsung SWA-9500S" itself - they are both the same wireless rear speaker kit from Samsung. The addition **"/XN" is only a version/region identifier (model code) as used by Samsung and dealers - but not a different feature or function.
The Samsung SWA-9500S rear speakers only work with certain Samsung soundbars, mainly newer Q-series models from around HW-Q700A, HW-Q800A and HW-Q900A (or similar series models). They are not compatible with all Samsung soundbars (e.g. not with some S or B models).