AF are designed to push air through the case and SP are designed to push air through a radiator. So the SP120 is designed for radiators and possible the front fan/fans on the case to push the air through from the front of the case. The AF120 fans would be used on bottom/rear fan spaces to let the air push out of the case.
This video shows how the famous tech youtuber JayzTwoCents has 12 Corsair fans on his old beast pc and how the fans are almost silent. He shows his fan setup and where he put the SP and AF fans.
AF are designed to push air through the case and SP are designed to push air through a radiator. So the SP120 is designed for radiators and possible the front fan/fans on the case to push the air through from the front of the case. The AF120 fans would be used on bottom/rear fan spaces to let the air push out of the case.
This video shows how the famous tech youtuber JayzTwoCents has 12 Corsair fans on his old beast pc and how the fans are almost silent. He shows his fan setup and where he put the SP and AF fans.