Best I can guess on the overlay (I don't use Maps enough myself to really know!) is to delete Google search history or delete (or even block) their cookies, or maybe do both (I take a number of steps on the laptop to stop tracking, so I can't really speak to what to do once it happens, but setting CCleaner to wipe everything and setting your browser to dump everything upon exit should clean up whatever can't be prevented).

Opening Maps in a Container (Firefox) might also help (or might not, but you never know until you try). I don't know if Google tracks users across the Web like Facebook does (via a tracking pixel) but containerizing things can't hurt, especially if that's the case.