Matthev I am using the BIOS you sent me for RX580 GIGABYTE with 8GB Samsung memory. I am getting around 29.5MH/s now. My core is set to 1300 and memory to 2000 like you said. Can I push anything more out of these cards or nah? If so how?
It depends, I don't really know what I sent you 
But Samsung it must be Uber-Mix 3.1, you need to find highest memory clock speed with no errors or at lest with a very low errors. It should be running more. I can have 30+MHs with shitty Dual 480 8G and that's with stock config in claymore...where to find them?
are they different for different brands/memories?
Yeah it depends on memory brand! Read the thread, or PM me I have timings for all memory brands.are they different for different brands/memories?