Yes, it would still be in sight even with a concealed display. However, I don't think stealth is really that much of an issue. They're both tiny enough that you wouldn't notice it unless you were looking for it. Hard wiring so that the cigarette lighter adapter isn't dangling around definitely helps.
I did a
V1 concealed display setup in my Lexus IS250, maybe you can get an idea of what it looks like from the thread I created on it. But, I'm sure that someone has also done it on their Z. The main benefit to using a concealed display is to move the red lights out of clear view and down to somewhere only the driver could see it.