The width of the rear beam is the same, between the points where the brake drum / hubs bolt onto axle beam. The hubs and discs will add quite a bit of extra track to the 133, but the usual ET55 offset wheels on the RS133 will make this less than it would be with ~ET35 of the 1.2 models
Theres a torsion bar welded into the underside of the beam. On the Dynamique, this is 19mm diameter and 24mm on the RS133 cup (not sure if the non cup is smaller)