Layouts seems to be the combination of Styles and Folder Tab Groups. but in practical, Styles can actually include the lister layout too and it is giving more control at the preference console. Styles is more flexible in choosing what to include. The idea of layouts, styles, folder tab groups and folder format is actually a bit confusing to me, like what scenario are they for and it seems they have so many overlap in function?
Yes, there is some overlap. I only use one Layout, no Styles, just a few folder formats. I have several tab groups and toggle the panes via hotkeys. Others use 50+ Layouts. It all boils down to personal preference. Shifting from one concept to another is easy, so start and try things out, and see what works for you.
Layouts are generally for saving and later re-opening one or more windows.
Styles are generally for changing one existing window.