In HK you will find CX has lounges at both ends of the terminal (first and business on gates 1-5 and the same at the other end … don’t remember the number but say 50 to 60).

Your flight will most likely start at the later which means if you have sapphire or emerald status you can enter there and find food, showers and plenty of seating.

If you are emerald, near gate 1 you have a first lounge with bathtubs and slightly better food options. I wouldn’t bother too much as I would rather prefer to be just a few meters from my boarding gate than walking the 10-15min it takes to cross the terminal.

As for the seat, I cannot help much. The normal ones have the moving armrests so that helps but you may then struggle not bothering the person next to you (and if he or she happens to be “wide” too - and by that I mean any person that is not very petite- you may end up fighting for space). On normal seats you also have the issue of less legroom!