Tropopause is usefull for the FMS for atmosphere modeling throught which your flight is taking place.
The FMS will use delta ISA up to the tropopause then delta ISA equal to Zero above the tropopause.
Also note that Winds increase by 4% per 1000 ft below the tropopause and decrease by 5% per 1000 ft above the tropopause.
*Some* FMS units will do that.
Not sure what you mean by the wind rule of thumb with respect to the tropopause.