For normal installations both should be turned-on..
this gives you a lot of functionality: IVS on cams (for perimeter protection), AcuPick 1.0 (3d human/vehicle modeling for searching similar looking people/cars in saved footage from all cams), AcuPick 2.0 / mini Video Meta Data (human/vehicles snapshots with attributes - like women, middle age, white t-shirt, blue jeans, white car, Subaru brand)..
ps. please update both NVR and cams to latest firmware to get all AI functionality.