What rating of constant current LED driver do I need?
A constant voltage supply will output its rated voltage at any current up to the maximum it is built to supply.  If overloaded, it should shut down.  They come in standardised voltages, such as 12V or 24V.

A constant current supply will deliver whatever voltage it needs to, in order to push its rated current through the LEDs.  So a 1500mA supply will keep ramping up the voltage until 1500mA flows.  This will be subject to a maximum voltage that the power supply can deliver, such as 30V.

Selecting the wrong sort of power supply is liable to either overload the power supply or blow the LEDs.

If you're using 12V LED strips, then you need a 12V constant voltage supply, with a wattage rating high enough for the sum of the wattages of all the strips.