LED specs for atx power on status
Out of all the manufacturers I have seen Intel to follow a standard. Few manufactures like Asus, Gigabyte and others follow them also in their motherboard designs.

While Asus follows the Intel standard on their micro-atx cheap boards, I have seen them use an intermediate connector to make front panel connections easy. It was called Q-connector. I believe that the first picture in your post if of Asus motherboard with Q-connectors.



I believe that the LEDs used in such cases are 5v LEDs with built in resistor.