...maybe in the next sentence stating what he sees in this overlay
There are potentially hundred of different electronic devices and files networked to any regular PAN.
If you wish you can choose to see all of them at once... but this tend to be a bit overwhelming.
Most people instead choose to filter out icons that they are not particularly interested in at the moment.
According to what we've been saying, he already knows what the devices are...
He knows that it is "some sort of firearm". Iconography is very intuitive and helpful when it comes to things like this.
This is no different from if the street samurai would have just glanced over the guard using his regular perception.
SR6 p. 173 Icons
Icons generally follow guidelines to resemble the class of object they represent.Looking at the icons more in detail reveal more detail, such as the weapon being "a Colt America L36 light pistol".
But this would the street samurai also find out if he spend an observe in detail action with his regular perception.
You understand the difference between what is immediately obvious that you pick up when just glancing over the scenery and what you can find out if you spend the time and effort to observe something in detail?
In most cases you can just treat matrix perception as you would treat regular perception...
...the security guard would not have a persona since he's not also in VR.
You will normally show up with a matrix persona icon as soon as you connected to the matrix (no matter if you are in AR or VR). Most people you run into on the street (like Bob the security guard) will pretty much always be connected to the matrix (= having a PAN / a persona icon).
Quick question on daisy-chaining commlinks to have the team decker protect them: What does this look like in the matrix?
Each commlink, cyberdeck or RCC used to access the matrix with typically represent a person. No matter if they are part of a larger network or not. The Iconography state that they will be represented by some sort of sapient being;
SR6 p. 173 Icons
Icons that represent personas (see Personas, Devices, and Attributes, below) are supposed to be some sort of sapient being, though that can still get pretty wild; cat-headed people, humanoid trees, and shapeshifting robots are all forms you might encounter, along with the (relatively rare) people who just like to look like themselves.Yeah I think it's still technically unclear whether there is any difference between commlink icon and Persona. Is it POSSIBLE to dataspike the commlink specifically, without affecting the Persona matrix CM?
It seem as if the persona's CM will be the same CM as the device (commlik, RCC, cyberdeck) used to access the matrix with. If this specific device (=your persona) is bricked then you will be booted out of the matrix (possible suffering dump shock).
There isn't a meaningful mechanical difference between a Persona Icon in AR and a Commlink Device Icon
As I see it....
A wireless enabled but unattended and unused commlink will be represented by a small device icon (that visually probably look similar to that of a small smartphone). It is immediately obvious that this is a device.
A wireless enabled commlink that someone is actually using to access the matrix with will be represented by the users's matrix persona - which look like a human sized sapient being of sorts. It is immediately obvious that this represent a persona (but I guess it might be tricky to tell if it is actually a real user, an agent program, a sprite or an IC etc)
In my imagination, if a user is carrying a commlink but not using it's AR/VR capabilities, then on the matrix it would just appear as a device icon (not a persona). As it moved around, the icon for the commlink would just bob around. 
Even back in 2020 most people were connected to the internet via their smartphones 24/7.
Not often someone would not be "logged on" to their smartphone and just carry it with them as dead weight.
It is pretty safe to assume that most people in 2080 will be connected to the matrix....
You kinda need to be if you want to see augmented reality and if you wish to broadcast your SIN etc.
This is from SR5, but I don't think this part changed:
SR5 p. 222 Life with a commlink
Stores have their logos blazoned in 3D above their door, restaurants offer animated menus complete with tantalizing images of their food, street names hover over every intersection, decorators use AR objects to spruce up interiors, all viewable in AR for anyone who has the capability, which is pretty much everybody. The unintended side effect is that things can look a bit dingy when you turn off your AR display, but that’s the price of progress.