My initial thought would be only if the RGB channels were equal.
Second thought is to only apply RGB effects to a RGBW string, taking into account the 4th channel is white (and not used for current effects). A separate effect could be made to only effect that 4th white channel, and could be layered with other effects on the timeline if wanting to use the white channel. Perhaps making a checkbox for the existing node types (all the different color order types) that change the string from RGB to RGBW.
I'll search around again on my PC for previous discussions. Searching on my phone thru taptalk is a nightmare.