IOW, more of the same old crap. I haven't read the articles yet, but I'll bet they're going to be National guard, so Governors of "Blue States" can veto the use of "troops" from their states, like California.
A couple hundred "support personnel" has been done before, and we already know it's not enough.
ETA: I read the articles. Mattis not saying where the "troops" are coming from, so I strongly suspect I'm correct: Not Regular Army, but National Guard. SSDD.
I suspect you are correct and they will be unarmed. Now, the migrants will be aggressive and belligerent, but they're not the ones to really fear. If we make any effective moves to shut down border traffic the cartels will act. And our troops will lose.