I agree, the WS2811 strips have 3 LEDs controlled as a single pixel. WS2811 Technicolor (new rev!!) do not have this problem, the IC controls only the single LED in the node.
I've used the WS2812B flex strips, and they work very well, and each LED is separately controllable. In the pictures, look for cut-lines on the strip... if you can cut between each LED, then you know that that LED can be controlled separately from the other LEDs.
I also use TM1804... and they are good... when you don;t have a bad batch.