Maybe not the shape. But you could definitely work out the size, anything weird about them, and such. I asked her what she'd do if she saw a naked woman dancing in front of her. So yeah.
I'd agree on size, and maybe rough shape, but I guess it would depend on the "deformities".
Jack explicitly says that he was on hand when someone smarter (Parson) invented it. Parson saw the sex appeal of the archons. He then thought of a tactical use for it. Others don't know about it, as Parson invented it. That suggests it's not a normal tactic from the rule book, not a magic with some recognizable effect, but just a rule abuse- archons are attractive because they're based off Charlie's angels, soldiers are weak willed and like to look at boobs, so that non magical effect can be used without expending any juice, and from a hex away.
Zak3056 addressed the plan part.
And page 7 seems to clear a lot of this up - Jetstone's forces, or at least some of the more canny ones, are fully aware of what a flash mob is and what it does. We can see what look like actual flashes of light, and indeed nothing at all can be seen in the hex the flash mob is covering, and as troops leave it they become visible again (in this case the illusory ones). It seems magic is definitely an aspect of the flash mob.