Although Z2-ATX-120 adopts 20pin ATX connector, it can be plugged into the 24pin ATX connector on motherboard. You are suggested to carefully plug the 20pin connector of PSU into the 24pin ATX connector on motherboard as the connector has fool-proof design.
Both Z2-ATX-160 and Z2-ATX-200 use single 12V DC input. Z2-ATX-160 uses electrolytic capacitors for cost-performance tradeoff, has smaller board size (56mm x 21mm), and can deliever maximum 160 Watts power output. While Z2-ATX-200 uses solid tantalum capacitors for longer life, has bigger board size (56mm x 26.6mm), and can deliver maximum 200 Watts power output.