Your undervolt is working but it is limited by the amount of your cache undervolt.
Set the core and the cache equally to -80 mV and run Cinebench R23 for a test.
Now set the cache to -80 mV and set the core to -180 mV and run Cinebench R23 again. Is there any difference in performance? Older CPUs used to see a small boost in performance when setting the core to a bigger number compared to the cache. For some CPUs, there might not be any difference. If you do not see a difference in R23 then leave the core and cache voltages set to the same values.
Sometimes when you undervolt the CPU will run faster so power consumption will be exactly the same. If power consumption stays the same because of power limit throttling, your temperatures will be the same.