Flickering can be a issue when your cycle_time of your LED's , extruder a somehow interfere with each other
Check which item either hotend or bed see causes you flickering with your LEDs by turning you LED's on, then turn on your hotend,
if one or the other flickers add "cycle_time: 0.01" to the LED and "pwm_cycle_time: 0.01" to the extruder causing the flickering
If its your bed it's another similar config, I can't recall off the top of my head but that would be similar to pwm_cycle_time or just cycle_time