It depends on what you're mining.
To begin with, click the gear wheel icon (settings)
and check "Unlock Voltage Monitoring"
and uncheck "Syncronize similar GPUs"
Now overclocking
For Etherium:
Power Limit: from 55% to 75% - 55 for energy (cost) and less heat (noise), 75 for full crop.
Core: +150Mhz (notice the voltage and temp drop!)
Memory: +180 as a start.
If you get 24-25Mh/s with these settings, then you've maxed it out.
For Hynix memory usually absolute max is 22.
If you get less, start bumping +100Mhz on Mem clock every 10 minutes.
when it crashes, reboot and use the last stable mem clock.
Repeat the same for each card.
Please provide feedback!