First thing of the vectorscope that is realy amazing: you have a ‘skintone’ mark. No matter which ethnicity the skin tone will match that hue: skin color is melanin and blood. all melanin and blood have the same hue. consider those pigments in an ink and you grasp the concept instantly.
then, with that, you can also instantly correct white balance of any scene adjusting only the hue slider until the skin tone matches the proper line.
there are other ‘known lines’: foliage green (all chlorophyll is the same so most greenery will fall near there), sky blue, pure RGB and CMY (the little squares in the graph) .
here you have the rgb waveform, parades (which is the same of the waveform bur split in rgb), vectorscope and histogram.
with the waveform you can see where in the image there is clipping (the x axis is the image position, the y is a intensity plot of all pixels in that column), how is the general luma and contrast and many other “tricks”
with these tools you have info other than eyes to gauge the image balance so you can edit quite well and/or faster with a less than ideal color fidelity and ambient light: the workflow may have, then, a more technical approach than artistic ‘feeling’.
there is one motto in the video world that goes something like this: “don’t trust your monitor: it may be lying. Trust only the scopes.”
I agree that vectoroscopes and waveforms are much more useful than a regular histogram. I know one raw converter which supports a basic waveform view – darktable. It also offers a very useful raw overexposure indicator. Another image editor which has vectoroscope and various kinds of waveforms is Affinity Photo: