All double glazed unit's, no matter how big the "air gap" in the middle are all made the same way.
Please say most (never say 'all'), because....you are wrong, and probably not old enough to remember the first efforts at double glazing for domestic properties
Taken from Wiki: A product known as Vacuum Insulated Glass (VIG), or evacuated glazing, can be used to drastically reduce heat loss due to convection and conduction.[6] These VIG units have most of the air removed from the space between the panes, leaving a nearly-complete vacuum.
Many originally single glazed panes were replaced by the early variant of this, being of minimal thickness to fit the single glazed window rebates. Certainly not a perfect vacuum (thin glass would obviously bend under the forces, unless a very small unit), but nevertheless claimed (in their day) reduced acoustic transmission, as well as reduced convective and conductive losses. Not sure how good the modern equivalent is, but they do claim the insulation value similar to a 'thick insulated wall' I somehow feel they may be exaggerating a little, but that seems to be the order of things.
Many eventually leaked and misted on the inside, making them quite unsuitable as window glazing.
They do say 100mm is far better for acoustic insulation, but I would not be sure of the optimum. Certainly my secondary insulation (about 75mm inside the double glazed windows) makes a huge difference acoustically.
reflects the heat back into the room its installed into if installed correctly!
You mean it only transmits infra red of certain frequencies (or wavelength), just like the glass in a green house, only even more selective, so the thermal enegy remains within the room. Just like vacuum solar thermal collectors, then?