Can confirm that there'll be full meals, at least that is what's been offered in J for midnight departures out of GRU (77W) and GIG (763) this week. Salad and starter served together, followed by main course, followed by Sundae or cheese plate (you may have both if you ask nicely
)
And the seats are just almost the same as in the 763 - they may be a bit wider, plus there's a very outdated built-in IFE.