This is a quick reply (maybe someone has time to jump in later) as i have a lot to do today.
That said the 1k8 is bright. The higher you go the less bright it is up to about 4k7.
If you attached the LED to power and did not have at least 1k8 you would likely blow the bulb so fast you would not even notice it. I also keep a coin battery (3v to 5v) handy for checking LEDs in a pinch.
I cannot make out the wiring or Buff N Blend details using the photos available to make any exact deductions.