A buck LED driver will have a very specific voltage range. With a max and min V_f. LED CC drivers are sold by their wattage and max voltage.

For example this is a Mean Well 120 Watt driver available in various voltages. Each voltage model has a range of V_f supported.

None of which will work for you becasue your V_f is too low. The 12V min is 6V.

A higher V_f is usually more efficient. It also helps to use a V_in not too far over the V_f.

What would be your V_f if you wired all the LEDs in series?

I limit the string voltages to less than 48V. typicality 16 in series for white, blue and green, and 21 in series for red, orange, and yellow.

I NEVER power two parallel multiple LED strings with a CC driver. I have tried many times with various string and never did the current balance between the two strings. Closest was a 45/55 split.

I am using a buck and a cheapo power supply

When all the LEDs have the same V_f and the desired current is constant, a CV supply and resistors can be an excellent solution. With the correct constant voltage you can get better than 98% efficiency from the resistors. It depends upon how closely you need the radiance or irradiance of each LED to match. Even with the same current flowing there will be a variance in output intensity between each LED.

This would probably work better if you had 8 sets of 5.6V pairs all wired in series for a total string V_f of 44.8. You then use a 48V CV supply and a 4.3 Ω 4W resistor for a minimum efficiency of 94%. With a good CV source you can adjust the output voltage and resistor value for even better efficiency.

If you were to use a 5.7 V CV source and 5.6 V_f. This would require measuring the V_f of the LEDs at 700 mA after they reach thermal equilibrium to calculate the resistor. And use quality LEDs from a manufacturer that specifies the min and max V_f where the range is not too large.

Running all LEDs in a single string with a singe CC source, is generally the best way to go when you want the same brightness from each LED.

In some projects I use an inexpensive 48V CC driver made with a TI LM3414HV tweaked to 97% efficiency powered with a stable high efficiency CV source like a Mean Well HEP at 96% efficiency. Each driver powers a sting of 16 white or blue or 21 red for horticulture projects. I need current adjustment as the plants grow so resistors will not work well in most projects.

A buck LED driver will have a very specific voltage range. With a max and min V_f. LED CC drivers are sold by their wattage and max voltage.

For example this is a Mean Well 120 Watt driver available in various voltages. Each voltage model has a range of V_f supported.

None of which will work for you becasue your V_f is too low. The 12V min is 6V.

A higher V_f is usually more efficient. It also helps to use a V_in not too far over the V_f.

What would be your V_f if you wired all the LEDs in series?

I limit the string voltages to less than 48V. typicality 16 in series for white, blue and green, and 21 in series for red, orange, and yellow.

I NEVER power two parallel multiple LED strings with a CC driver. I have tried many times with various string and never did the current balance between the two strings. Closest was a 45/55 split.

I am using a buck and a cheapo power supply

When all the LEDs have the same V_f and the desired current is constant, a CV supply and resistors can be an excellent solution. With the correct constant voltage you can get better than 98% efficiency from the resistors. It depends upon how closely you need the radiance or irradiance of each LED to match. Even with the same current flowing there will be a variance in output intensity between each LED.

This would probably work better if you had 8 sets of 5.6V pairs all wired in series for a total string V_f of 44.8. You then use a 48V CV supply and a 4.3 Ω 4W resistor for a minimum efficiency of 94%. With a good CV source you can adjust the output voltage and resistor value for even better efficiency.

If you were to use a 5.7 V CV source and 5.6 V_f. This would require measuring the V_f of the LEDs at 700 mA after they reach thermal equilibrium to calculate the resistor. And use quality LEDs from a manufacturer that specifies the min and max V_f where the range is not too large.

Running all LEDs in a single string with a singe CC source, is generally the best way to go when you want the same brightness from each LED.

In some projects I use an inexpensive 48V CC driver made with a TI LM3414HV tweaked to 97% efficiency (switching freq. and inductance) powered with a stable high efficiency CV source like a Mean Well HEP at 96% efficiency. Each driver powers a sting of 16 white or blue or 21 red for horticulture projects. I need current adjustment as the plants grow so resistors will not work well in most projects.