You can test by varying the Red only on one of the “white” LEDs in your segment (the odd ones?) and then try varying Green only and Blue only
No, it doesn’t work that way. Any single channel color (R, G, B) gives the same brightness on the “white” segment, any pair (C, M, Y) gives slightly brighter light, and white is the brightest.
Last weekend I’ve migrated one more Govee outdoor LED string to WLED, of different model, and its setup is even more challenging: it again has two chips/LEDs per unit, but White LED’s brightness is inverted: it’s OFF when brightness is 100% and OFF when 0%.
Govee probably simply optimizes their designs, using same WS2811 chips, controllers, wires for many products, even by using additional WS2811 chips to white-only LEDs.
I can live with two segments, one for RGB another for White, the real limitation is that I can’t get the full brightness/contrast when White segment is OFF, and it’s quite tricky to use any effect utilizing both segments. Solid colors are easier, as I can tune both segments to get the desired color/brightness.
So it would be great to somehow compensate brightness of each RGB LED with the neighbor white LED in more automated way.