The 5SU9304-0KK25: The 25 A rating at 30 °C tells you the continuous current it'll carry in a typical 30 °C panel environment. That derates to 23.5 A at 40 °C and 21.75 A at 50 °C — so if your enclosure runs hot, you need to account for that drop. It's a 1P+N RCBO, meaning it switches the live pole and protects against overcurrent and residual current (AC type,) on that pole, while the neutral is switched but not protected. The 18 mm width takes up one modular space on the DIN rail, so you can pack it tight in a distribution board.
IP20 with conductors connected means it's for enclosed panels only, not washdown or outdoor duty.