We must consider that every company has a different layouts and configurations for its aircrafts. I have visited ,B777, A330, B737 who looked completely different from the ones I use to fly. Even the galleys and number of toilets may vary. I can remember having visited 2 aircrafts side by side, a B767 and a B777 belonging to different companies, and the B767 carried more pax than the B777 (no First and Business, and minimum pitch on the 767).