a.) When setting "/gamerule doMobSpawning" to "false" in-game or in the menu, entering the nether and walking or teleporting to a Bastion_Remnant of any type, Piglins and Hoglins or Piglins and Magma Cubes (treasure room) will spawn once upon loading the chunk regardless.

b.) Sometimes, when in Creative, you can hear rain (and potentially thunder) in the backdrop.

c.)? When entering the Nether in survival or creative, overwordly music will continue to play until the track is over. Don't know if this is a bug or intentional.