I've been in an F seat (quite by surprise) on a PEK-NRT (was expecting 767 but got 777 for some reason that day). BP said C.
As to the lounges, the NH lounge is open as early as can be, and I'm pretty sure the showers are too. Certainly even the C side of the NH lounge beats the pants off the UA IFL in terms of food, ambiance, etc.
Plus, Noodle bar, Sake bar, Fauchon Chocolate Ice Cream!