I've been trying to sort this all out. There's been some minor discussion and I summarize like this:
Indicator Applet Complete
Complete as opposed to individual categories like Application, Messages, Power, Session and Sound found in can't-permanently-disable-them Startup Apps. Or a plain applet vs Appmenu as listed in Add-to-Panel.
I sense this is being deprecated. I'm guessing some older programs use this and may not be compatible with indicators?
At this point, my old staple Parcellite (clipboard manager) always shows twice in panel layouts Familiar and Traditional (and likely others). It's obvious one appears from each. Operation is different for right-clicks. I removed Notification Area and all seems well so far.
I tried the opposite (only Notification Area) but I get one reboot to turn off the startup apps that screws this up. Looks like it also works, however.
Have I got this summarized correctly?
Why are both of these in the default Traditional and Familiar panel layouts?
What's the consequences of removing Notification Area?
Why can't Indicator startups be permanently disabled (just for testing)?