Hello, a medium to good air cooler is actually sufficient to keep the processor in check. Of course, it would be advantageous to cool the CPU with water if the enclosure is quite cramped. But as I said, only in very special cases.
Arctic Freezer 34 CO (15.70 cm)
Alpenföhn Cooler Alpenföhn Ben Nevis Advanced (15.90 cm)
These will do by far.