LED lights themselves can require either constant current or constant voltage power supply, depending of their types. Transformers are certainly available for both, but you always have to check this detail with your supplier, otherwise you can easily ruin the low voltage products at the installation. The performance of the power supply simply has to be higher than the total performance of the LED lights running at it. Always allow some wattage for overrun, and do not forget to encounter the consumption of dimmers, controllers and amplifiers connected to your system.

It is best to purchase power supplies which are protected from overload, over voltage and over temperature,but depending on the place of installation a waterproof function can be handy too.

In conclusion, there are far too many types of power supplies to buy anything without checking with your supplier. Never buy power supplies which are not particularly made for low voltage LEDs, and even then check whether its features match the requirements of the LED lights you are buying.