Check for compute switch in the driver, by default it is NOT set to compute.
You can try much higher mem clock. It is usually safe to try 2150, even more for select cards.
I have experienced performance degrade when undervolting fail to set up, but not that much really. Check actual core and mem voltages and try to set to 950 mV and lower.
Go one at a time and check for results.
27 is pretty low for RX570, try to find better bios settings.