A sector is a physical (smallest) chuck that data can be stored on. I believe it can be changed through a low level format (this is usually only done by the manufacturer). A cluster is a logical grouping of 1 or more consecutive sectors (always in increments of power of 2s). Sectors you shouldn't really ever need to change. You can adjust cluster size to match common file sizes you will be dealing with which may improve performance in spinning disks. You may want to go with a different filesystem like XFS which is more performant than NTFS