Try Aug 23 drivers + this bios:
https://www.miningtweaks.com/sapphire-rx-580-nitroplus-4gb-elpida-bios/ (Elpida)
I get 30MH Eth solo mining, 29.3 with decred/lbry, 790H/s Cryptonight, all with Claymore.
My cards have Elpida memory as well.
By far the best value in a mining GPU so far!
I undervolt and overclock directly in Claymore:
-cvddc 825 -mvddc 825 -cclock 1150 -mclock 2050 -powlim 0 for ETH.
If you have a rig, i.e. several cards, set Windows virtual memory to 16 or even 32GB.
Also, try setting PCI-e to Gen1 in mobo bios, sometimes that solves some issues as well, don't ask why.