Do I still need a resistor in this LED series design?
LED forward voltages can vary some - enough that it would be difficult to set a precise current with them merely tied in series across a fixed voltage. Total Vf for the string can vary by several volts. You could very easily blow up the string just tying it to the supply as you’ve shown.
So, yes, you should still have a dropping resistor.
Even better, consider a constant-current driver. This not only would protect the LEDs from overcurrent, but would give consistent brightness despite variations in Vf.
There are switchmode constant-current drivers that can do this efficiently and for low cost, that also support PWM dimming.