TYPICALLY, it applies to stimulants. Notice that "typically" is capitalized.
A real world example:
I really should be sleeping right now, it's about 4 AM, but I'm literally too strung out on stims. It has me up at this stupid time, busy thinking/being paranoid about things that are barely worth my time. The only reason I'm able to realize, and thus admit, this, is because I'm drunk.
However, I have been "strung out" from opiates before. This only occurred when I was going about my day, but had the misfortune of fantasizing about my next dose. Of course I was on somewhat of a regimen, but the mere thought of another taste entering my mind would basically ruin the rest of my day.
In my situation, all I had to do was wait until about 5 PM, and I would be home and able to take my next dose. But if I had the misfortune of even THINKING about how much easier life would be if I had that dose NOW at 2 PM, then for the next 3 hours, I would be extremely irritable and rather arrogant. Kind of like:
Sober Dude: "hey so what do you think about that last assignment?"
Me: "That last assignment!? Fuck that shit! That shit was a waste of fucking time, and to be honest, a waste of all of our fucking time in general. Fuck that shit."
The way that usually ends is that someone perceives that you're far too aggravated to continue a conversation with.
Now, you mentioned benzos, but I don't even want to get into the benzo interpretation of "strung out." It's more like being a paranoid freak who feels like any moderate social interaction could be their last, due to a sudden anxiety induced heart-attack in the middle of a conversation.
You said to work with you for more details, so if this isn't enough, then I don't know what is. Especially because this is all 100% from 1st hand experience.