1. Win10 does not require any special mining drivers. Just download new from site.
2. You have to turn on compute in drivers option.
3. You have to use rigth command in bat file, for solo mining. -asm 2 parameter is required for Claymoor's miner.
4. GPU freq. must be 1150-1200 mhz, memory 2k+ (depends on memory manufacturer)
I have 29.6 mh/s from my RX574 (1174/2020).
You should include the bios mod because it has a lot of influence to increase the hashrate of rx 580 and it should be hashing around 29.5-31.5 mh/s
And i think even its 8gb or hynix memory type it should hashing at least 29 mh/s
And not all driver woks honestly there are driver that honestly not giving you a good hashing rate.. blockchain driver or crimson relive drive would be good alternative or test every driver lower or latest.. and test if your hashrate increase..