Inca returns to its Civ VI identity of turning Mountains into a genuine growth engine — settling in terrain every other civilization avoids is the entire strategy, not a side benefit.
"Apus" lets Inca work Mountain terrain directly for Food and Production from the very first turn, with further Food increases in later Ages. After completing the right Civic, Cities with enough worked Mountain tiles can generate Homelands Treasure Convoys, and Inca gets increased Production toward its associated Wonder.
The Chasqui is a unique Scout with increased Movement and Sight that can see through Mountains and Rough terrain. The Warak'aq is a unique Ranged unit with high Movement that ignores Rough terrain penalties and gets increased Combat Strength attacking from Rough tiles — a genuine mountain-warfare specialist.
The Terrace Farm is Inca's unique Improvement, providing a high Food yield; it can be built on any Rough terrain without a River or other Feature, though it benefits most when placed near Mountains. The associated Wonder, Machu Pikchu, must be built on a Grassland or Tropical Mountain tile and grants Gold plus Culture and Gold adjacency to nearby Buildings.