If you're hanging a ceiling, then you are probably more worried about the pull strength (straight out of the mounting material) of the screws, rather than the shear (sideways), compression (push) or tensile (stretched) strength of the screw itself. If driving into wood, the type of wood fixing is going to have a lot more bearing than the respective strength of the screws.

On the face of it, 36kg/12 screws = 3kg per screw. If the mounting surface can grip the screw sufficiently, any 5mm x 50mm screw will support this easily, in any dimension.