To the commlink in head vs seeing in AR, read over
this thread.
As to seeing in AR in general, you need to have some form of AR visual interface (image link in glasses, contacts, goggles, or cybereyes; or a sim-module). At this point, you will see "AROs" pop up when you are in-range of them (fluff-wise, they appear to know "where" to appear in your vision, a menu above the table, for example, but how to explain this in terms of mechanics is more elusive). As to seeing nodes and other matrix specific info via AR, these are handled as pop-up windows on the "screen" of your vision.
Imagine everything you're looking at on your computer just floating in the air in front of you. You could "re-size" a window and move it to your peripheral vision (using AR gloves, DNI, etc), you could change it's transparency to see past it if it was too important to minimize (trid-call from mom, perhaps?), and so on and so forth. Most nodes would still appear sculpted (think video game interface), unless you over-rode their appearance to just give you a textual / 2D view (like this forum).
You're spot on about Smartlink, it's an AR interface with your gun, to work you must have the extra "smartlink" hardware in your AR-viewing device, as well as having a smartgun.
In all cases, unless you use a holo-projector (comm-link screen), AR is either projected over your vision (glasses, goggles, contacts, cybereyes) or generated inside your occipital lobe (DNI). At best, a person would be able to tell that you had AR screens up based on the light display of your glasses/goggles, but in general, I'd rule that they can't make out anything you're actually viewing. After all, the projection on your glasses/goggles is being generated to be viewed by your eye, at a fairly close range behind the lens, not by another person some distance in front of the lens.