I always take Xanax before presentations. The trick is to take the exact right amount so that it reduces your anxiety but you don't starting nodding off like you just booted a bag of dope or something. If I take too much I just want to lay down on the couch and pass out and can't think straight. If I don't take enough it does absolutely nothing. You have to know what the appropriate dose is for your body and tolerance level. So you have to try taking it ahead of time to figure that out.
Also, you have to know how it will hit you and when. I usually take Xanax sublingually because I know it will relax me within an hour. If I swallow it its more like 2 hours. Xanax usually peaks in your system about an hour after you first start to feel it. That is when you want to be giving your presentation. So you have to time that right. So you can certainly use Benzos for presentations you just need to experiment with it first to determine the correct dosage.
Everybody knows you only live a day but it's brilliant anyway