Upper deck configuration varies by what the paying customer orders, whether from Boeing or from ancillary equipment manufacturers. Flat bed sleeper seats, business class seats, economy seats; bunk compartments separated by walls and doors, or bunks separated by partitions and curtains.
The max occupancy is limited by the number of inertia escape reels. If you add 2 reels, the occupancy could be ten, provided each seat, each bunk [and each lav] is equipped with oxygen mask. And yes, I have seen at least one converted pax bird with two (2) functioning lavatories upstairs.
The short answer is that there is no upper deck, global fleet configuration standardization.