There is a choice of around 10 different rear shocks for both models, all with different part numbers - it depends on engine capacity, diesel or petrol etc.
As far as I recall, the 206 ones are heavier and longer, but I haven't compared them side by side!
Regarding the adjustment, all this does is affect the rebound of the shock, and a good enough guide is to set to halfway (on both sides, naturally).
Other adjustments will give a softer or harder ride.
John