...but I've got a new icon to the left of my Safari address bar….
Me too, although I can't determine its purpose. It seems redundant. If I enter a search in the window it presents, I get the same results as I do when conducting the same search in the normal way.
I think you're misunderstanding StartPage.
My understanding is that when you search via the window presented when you click on its icon you get the same Google results you'd otherwise get, but your "identity" is blocked.
You don't see it in the pref pane because it's not a pref, rather it's a non-pref option.
