Boiled it down to minimalistic piece of code to avoind any sideeffects...

Here is a link to 2 different Atom Lite pieces running exactly the same software as shown below.
https://photos.app.goo.gl/KBm54aqW5LbtxsWq7
This video shows them side-by-side.....
They dow not in any direction behave at least a little bit similar.....

Any ideas anyone?

This is running on the Atom Lite now:

#include <Arduino.h>
#include <LiteLED.h>

// Choose the LED type from the list below.
// #define LED_TYPE LED_STRIP_WS2812
#define LED_TYPE LED_STRIP_SK6812
// #define LED_TYPE LED_STRIP_APA106
// #define LED_TYPE LED_STRIP_SM16703

#define LED_TYPE_IS_RGBW 1
#define LED_GPIO 27
#define LED_BRIGHT 100

static const crgb_t L_RED = 0xff0000;
static const crgb_t L_GREEN = 0x00ff00;
static const crgb_t L_BLUE = 0x0000ff;
static const crgb_t L_WHITE = 0xe0e0e0;

LiteLED myLED( LED_TYPE, LED_TYPE_IS_RGBW );

void setup() {
myLED.begin( LED_GPIO, 1 );
myLED.brightness( LED_BRIGHT );
}

void loop() {
myLED.setPixel( 0, L_RED, 1 );
delay( 500 );
myLED.setPixel( 0, L_GREEN, 1 );
delay( 500 );
myLED.setPixel( 0, L_BLUE, 1 );
delay( 500 );
myLED.setPixel( 0, L_WHITE, 1 );
delay( 500 );
}