My favorite seat was actually on the lower level. The furthest forward window seat on either side (usually 1A or 1K) was unique. It’s directly below the cockpit and the fuselage is curved at that point so you get the almost pilot-like view out the window of facing forward.

https://www.seatguru.com/airlines/Lufthansa/Lufthansa_Boeing...

On most airlines the upper deck was originally used as lounge space, and then later for first/business class, which may have helped with the poshness you experienced.

In the early-mid 2010s I was fortunate to fly several times on the upper deck of an EVA Air 747 (SEA–TPE). On these planes, the upper deck was regular economy in a 3x3 configuration. It felt like a miniature 737 inside the huge 747, cozy in its own strange way. They also provided slippers and the window seats had a fun shelf/storage space, making it feel all the more special.

Qantas apparently had an unofficial 'no kids' policy for the upstairs business seats.

Also the storage bins along the walls due to the sharp angle were awesome if you had a window seat.