I am currently playing through BG 1 to refresh my memory.

The world felt lived in and alive from the beginning, but why?

Well we don't start at Candle-keep or an established background, so that immediately needs to be compensated for in big or small ways.

The sound effects are spot on: crickets at night, rocks falling near rock formations, background animal sounds in abundance, and other miscellaneous. (BG3 should step up in this area).

NPCs (there can be small but important improvements here).