K4 Wireless Mechanical Keyboard (Version 2)

Re "Is there any way to boost the brightness of the backlight of the key itself?": Presuming it is already at maximum brightness by Fn + W (or Fn + knob (if the keyboard has a knob)), only by using keycaps with better shine-through characteristics That may be difficult for the south-facing LEDs on t

First reset to factory defaults Unspecific, but par for the course is resetting to factory defaults and reflashing the keyboard firmware. Though reflashing the keyboard firmware is risky business for the original K series with proprietary keyboard firmware (which includes the K4 V2). It is a differe

(K4 V2 is in the original K series. Only K4 V3 got QMK support.) It probably doesn't apply to the original K series, but RGB light off is a problem for some later Keychron keyboards.

Related: K4 V2 RGB backlight is really weak K3 Pro brightness fix (possibly others) Increase backlight brightness beyond default limit Keychron K1 Max RGB too dim Has anyone tried bumping up LED current and survived to tell the tale? PSA: the LED's on the K3V2 are significantly more dim than the K3V

Re "can you increase the Caps Lock brightness?": Yes, drill a hole in the keycap Or get another keycap with better shine-through characteristics. But that will not be easy. Making the plate underneath more reflective may also be sufficient. The inside of the keycap could also be made more reflective