Basically just start with what you’re aiming to enable and work backwards (as you’ve started to do). With judicious use of grep find out where that symbol is defined. If it’s in arch configs for other arches but not your own, it’s probably that.
There may be better tools out there to do this, but in my experience just sleuthing it out a bit will answer your question. The Kconfig system can be complex, but the files are pretty readable.
GNOME 3 introduced the current shell paradigm where you don’t really have a start menu but a variety of searches, integrated indicators, per-app desktops with a dock etc.
Before, it was far more conventional experience like Plasma/Windows/Cinnamon are now. GNOME 2 was forked to be the MATE desktop if you want to check it out.