I personally really liked the system in PF:K, since i only played Pathfinder in homebrew settings and wasn't familiar with the World of Golarion.
Also having a comprehensive Codex with:
-Places (Faerun, Forgotten Realms, Baldur's Gate, Waterdeep, etc.)
-Characters/groups (People you meet and also important people for the setting, also Groups like Flaming Fist, Harpers, etc.)
-History/Events (Descent into Avernus events, Bhaalspawn events, Spellplague, Sundering, etc.)
-Gamplay mechanics (Attributes, Skills, Spells, Class Abilities, Action economy and so on, especially helpful for new players)