The only reason why anyone would want to use two 12V-2x6 cables is to have a PC with two Nvidia graphics cards but given that ...
With the ATX standard also came the ATX power supply (PSU), the standard for which ... the -5V rail was removed, and the -12V rail made optional. The ATX power connector with the mainboard was ...
The MSI MPG A1000GS and MPG A1250GS are not directly compatible with AMD's RX 9070 series GPUs, unless you get an adapter.