I like this chart but still I don't know what AWG is used for 400A : r/electricians
Package Code SBC-12-250, 12 American Wire Gauge (AWG) Size and 250 Feet (ft) Length on Spool Solid Bare Copper Wire On International Wire Group, Inc. (Omega Wire, Inc.)
Hard Core Copper Wire Electrical | Solid Copper Wire Electrical - Wire Single Core - Aliexpress
Electrical Characteristics of AWG Copper Wire | NAZ Solar Electric