Does the 400w flash have any requirements for sockets?

There is no requirement, just meet the rated voltage of the flash.

Flash is called flash in English and electronic flash in Chinese, also called high-speed flash. The electronic flash lamp stores high-voltage electricity through the capacitor, and the pulse triggers the flash tube to discharge, thus completing the instantaneous flash. The color temperature of the usual electronic flash is about 5500K, which is close to the color temperature in the sunlight during the day. Its luminescent property belongs to cold light type, which is suitable for shooting objects that are afraid of heat.

According to the explanation in the photography manual published by National Geographic, the flash index indicates the luminous intensity set by the flash manufacturer for each flash, which is usually set based on ISO 100. Flash index is usually represented by GN, which is the abbreviation of guild number.