Transfiguration Phoenix S cartridge - impedance loading recommendation?

If the internal resistance of the Transfig is 2 ohms, not 1 ohm, you might be slightly better off setting the input impedance of the Accuphase to any number above 10 ohms. This is only because you want ideally the input Z to be at least 10X higher than the output Z, for any two components where one drives the other. It primarily affects the efficiency of energy transfer, in this case signal voltage. The rule is rather plastic when it comes to phono cartridges driving phono stages, so I would not worry about it much, but maybe try 30 ohms or higher and see whether the system becomes a bit more dynamic or produces higher SPLs at lower settings of the attenuator. In some cases, where the inputs have some capacitance, the ratio also affects transfer of high frequencies. In the case of a bad mismatch, you’d expect some audible roll-off in the treble region. I doubt that would be a noticeable problem with your current choice of input impedance.