After many more hours of working I’ve encountered yet another issue that I am uncertain how to approach.
I decided to embed a colorchooserwidget in my application, rather than a color button and a dialog.
I really do like doing so, but the problem is that the color picker editor (not the palette, which I don’t need, nor the transparency) is way too big. I understand why and also respectively understand that I cannot obviously force it to be smaller (either via GTK calls or CSS). And I already spent plenty of time writing custom widgets and at that point I really need a quick and simple solution (because I am soon announcing the project globally with a working beta being made for my Patreons, but I am a bit past my schedule). This means I really cannot afford to write a custom color picker or subclass/override on it (as I see it’s not going to be as easy). Maybe later I will, but right now, I am just trying to follow UNIX philosophy (Release soon, release often).
It would have been nice and very powerful if I could choose color picker varients or perhaps an option to make it smaller. How it looks in GIMP is also not bad. I can choose between 16 million of colors but I cannot choose color picker variants or size (by reducing precision hence density)! 
Can anyone offer me some sort of solution as I am in a need of such a smaller color picker? (For some reason I also cannot find user-made custom widgets online)