for plan-A, can i tap my 400A / 400 MCM residential feeder that is off the main 400A service
to two 40 feet-away -located 200A sub panels thru 3/0 ????
or, as plan-B, just install a 400A distribution panel with main on the exterior wall of the house than,.......
(the 400A service is located at the corner of the property, stand alone, dettached)