ATX
The remote switch wire for an ATX or BTX power switch is typically connected to the motherboard's front panel header. This header is where you connect various front panel connectors, including the power switch, reset switch, power LED, and HDD LED. The specific pins differ depending on the motherboard model, so it's important to consult the motherboard manual for the correct connection.
The power switch.
Soft Power
soft switch
True
In both ATX and BTX power supplies, the remote switch wire from the case must be connected to the motherboard's power switch header or pins. This connection allows the power supply to be turned on/off using the computer's power button.
it is used to supply power to motherboard and other peripherals
There are usually a couple of small screws on either side of the switch. You'll have to take the side cover(s) and front cover off. You will need to trace the wires from the switch and notice where they are plugged into the motherboard. There is most of the time a triangle on the plug that connects to the motherboard, that triangle needs to line up with pin one of the "jack" on the motherboard. On some motherboards that matters, on others it doesn't. It isn't that hard, and there's no danger. The biggest problem is some systems are really cramped, and you have to be able to trace the wires.
It is to open the power-switch at zero current to minimize the looses during switching.
A motherboard is compared to a power strip or a mother.
There are no differences between the power connector of an AT motherboard versus that of a BabyAT motherboard.
To remove motherboard varnish, you can use isopropyl alcohol (preferably 99%) or specialized electronic cleaner. Soak a cotton swab or a soft cloth in the solvent and gently rub the varnish until it dissolves. Be careful not to damage any components or traces on the motherboard. Always ensure the motherboard is powered off and disconnected from any power source before attempting this.