The most interesting thing about Caffeine for me is that it can cause severe anxiety attacks in some people. Whether that's because they are responding to the physical symptoms or it has an effect on the brain really interests me. I enjoy a couple of cups a day but completely avoid energy drinks, you don't need to be an expert to know that a can of fizzy energy drink is going to contain a plethora of nasty chemicals which cannot be good for the body. My energy levels are very good and I have to have one of those large Costa coffees to really feel a buzz or witness any physical symptoms such as increased heart rate. In short drinking coffee in moderation is not dangerous.
caffeine + propranalol is a excellent combo, lots of energy and motivation but no high heart rate, or edginess.
coffee though probably contains more uncontrolled chemicals than energy drinks though, at least you know exactly whats in them you don't know fully whats in a coffee been to the molecule or more importantly whats sprayed on them, or baked onto them.
unless you wash it first which i don't think would work lol