The torsion bars only go in on one spline. You cant adjust the spring rate by fitting differently imo. If you tried to load up one bar on one side i can imagine a lop sided vehicle. I recall renault saying remove one bar to set the rideheight but it never seems to work well in practise
If the beam was correctly installed in the first place that is mostly true.
Spring rate is fixed, ride height can be adjusted by removing left and right torsion bars, setting the beam to the new position then reinstalling the bars, taking in account that there are only a few height values in that they can be inserted. (around 3cm steps I believe)
If it went all apart or mix-match parts like I did, then the ARB has to be indexed properly, and in that case the ARB can be installed in a few different spots, only one is correct.
I'll start dumping a few P/N so we can compile a nice list:
torsion:
????????????? 20.8mm R5 GTT/ Clio RSI and others with ABS
7700 804 336/7 21.6mm Clio 16V/Clio GrA
7700 758 855/6 23.2mm Express /Clio GrA/Clio GrN
7700 813 039/40 24.5mm Express Extra Load /Clio GrA/Clio GrN
ARB:
????????????? 22.5mm Clio RSI and others with ABS
????????????? 23.4mm Express (and R5 GTT)
????????????? 24.2mm Clio 16V/Williams
7711 126 160/1 25.5mm Williams GpA
7711 066 925/6 26.5mm clio 16S GrN/Williams GpA