Nikon FF/raw-only shooter here.

In the Nikon environment, you have to jump through some hoops to get the RGB histogram to more closely match the data being stored (essentially a profile where R=G=B, which gives the review panel a green cast). I use it when I know the color temp of the light I’m in (e.g. daylight) or I’m using a white/grey card (white for low light). I’m pretty sure Nikon is calculating the histogram from the part of the shot being reviewed (if you zoom in, the histograms change, allowing closer examination of a particular area. Dunno if that’s by design or an artifact of how they calculate.)

Anyway, if you’re a raw shooter, the important part of a histogram is the gap between the right edge of your readout and the right end of the graph itself. For ETTR, you want the gap as small as possible without the line crawling up the right edge. I stick to RGB because even one color ‘crawling up the right’ means I’ve blown out that color, something I can’t fix in post.

Why do I go through the pain of lugging FF gear around? Mostly so I can shoot in low light and still get decent detail. When I took the shot below, It was getting hard to see, so it makes a decent example of this. Also for night sky photography, but now that I’m using a star tracker, I’m not sure a MFT camera wouldn’t work as well. (Night sky shots are more about how much light you can gather in 15 seconds or less, a limitation form the planet moving under our feet.) Gotta say, if I go MFT, it’ll be Fuji.