Can you still buy a rx580 8gb and 590 at 350$ today? 30MH is assured but I'm not so sure about power consumption since Nvidia cards are my favourite in terms of efficiency, 60MH under 120watt is awesome to me this is why RTX3060ti is the king 👑👑👑
There are several things to consider in this situation.
What is your electricity cost?
Do you have restrictions on electricity consumption?
If electricity is expensive and you cannot consume more than 3 kilowatts, for example, then I would do a mining farm on more modern video cards.