The rear vortices have no purpose (they are just there because of the pressure difference above and below the rear wing).
The vortices which pass by the side pots are probably provoked by winglets on the front wing, which probably help keeping the low pressure region underneath the car (prevent high pressure air from traveling underneath the car).
They used to have sideskirts to seal the low pressure region underneath the car, but they were prohibited about 30 years ago.
