I may not be real, but I am a chemist!...I don't think there are any real chemists here ...
Conductivity of a salt solution depends on several factors. Most important is simply how many ions are in the water, since these are what carry the charges from one pole to the other. One mole of NaCl produces 2 ions, Na+ and Cl-. Magnesium or calcium chloride each give 3; 1 of either Mg+2 or Ca+2 divalent metal ions and 2 Cl- anions. So for a given number of moles dissolved in solution, magnesium chloride will be more conductive than sodium chloride. This also applies to freezing point depression, and explains why (in part) that calcium chloride is preferred over sodium for melting ice. (Lower toxicity to plants is another.)
Another factor is ionic mobility. A chloride anion might be more active than a sulfate anion, for instance. So not exactly equal conductors even if they are at the same molarity.
There are other smaller factors as well. Not worth digging into here.