If your Rhino units are set to metres, then Load is in Newtons, Strength for Length goals (springs) is EA/L (with Young’s modulus in Pascals).
‘Magnetic Snap’ is not intended as a quantitative simulation of magnetic behaviour - it just acts like a zero length spring that activates when the points are below a certain distance apart.
I go into more details about the dynamics here:
It’s useful to consider this in the context of what you are trying to do - whether it is form-finding, geometric linkages, finding accurate static deformations under load, or dynamics where you want accurate velocities, the requirements will be different.