There are 2 modes based on the color order selection, RGBW / GRBW which use the white element automatically, and RGB-W and GRB-W that don’t use the white element at all.
For RGBW support, white is automatic, and is borrowed from R+G+B values.
For example, if you had a color that ended up as (red=255, green=127, blue=32), then 32 is removed from each and sent to the white element, resulting in (red=223, green=95, blue=0, white=32).
WWA LEDs aren’t officially supported in that there aren’t any specific features for them. I’ve seen these in both WS2812 compatible protocol, and APA102 compatible protocol. You can still send these data using the rgb() API and doing your own calculations to mix the elements for desired effect.
Only 3 element RGB and 4 element RGBW types are supported. I haven’t seen any 5+ element addressable LEDs, not commonly available using one of the supported protocols anyway.
The output expander likewise is designed for 3 or 4 element RGB / RGBW WS2812 compatibles, and RGB APA102 compatibles.