Looks like I've solved the problem. The Sapphire Rx580 nitro + comes with dual bios, a 'quite bios' and a 'performance bios' which you can switch manually on the card. I changed to the 'quite bios' and I was able to overclock that. I guess the performance bios is locked in the bios to a certain clock that's why I couldn't change it. I used these proflies to overclock in adrenalin 2020:https://community.amd.com/thread/245338