Regarding the low benchmark scores: I suspect Apple disabled SMU firmware for the W5700X MPX module at the moment because there is some issue with Kernel Panics on boot when SMU firmware is loaded for Navi cards on 10.15.5 beta. Check
here and
here for reference.
If you are on 10.15.4 you can use OpenCore to inject those device properties on the W5700X until Apple fixes up their mess:
- ForceLoadFalconSmuFirmware with value 1
- PP_WorkLoadPolicyMask with value 32
This should give you expected Geekbench results. Just don't upgrade to 10.15.5 with those parameters. macOS will only panic then.