The principle of choosing an RCD for a 20 W LED floodlight

Hello! I am interested in the principle of choosing an RCD based on the example of my particular situation: I am going to connect a 20 W LED floodlight with a motion sensor via an overhead line (about 25 m) on a cable in a corrugation, to a tree. I want to connect it through a circuit breaker (bought at 6 Amps) and just in case paired with an RCD. The question is which RCD is preferable to choose: at 16A with a leakage current of 10mA, or a cheaper one at 25A and with a leakage current of 30mA, even within the same manufacturer, for example, Legrand? The question itself is not the choice of the brand, but the feasibility of the parameters. I understand that 25A 30mA is quite suitable. But I don’t understand enough materiel to be sure. Thank!