Mini LED Spots for Terrace Canopy

24 V, then at the same power the current is lower and you can possibly use a smaller cross-section. Ideally, cables made of copper with a sheath around them and with as many cores as needed. The cross-section is determined by the current running through it.

just take 24V lights and then select the appropriate transformer accordingly they also have a set with 12V you specify how many lights you want and receive the transformer with it in the photo it is a 12V transformer

I would either take a set or the transformer/driver recommended by the supplier. With a 12V set you can assume that it is properly coordinated. Then you have more than just one transformer/driver. Both options work. I would favor a 24V transformer/driver. Visually, you wouldn’t notice a difference compared to several 12V units.