I'm working on a story that requires travel at about convenient* speeds (see below). I want to keep this story as hard sci-fi as possible and I've heard about stuff like Alcubierre drives which sound like a good fit, but I'd also like to know what the pros and cons of such a method would be (for instance, I would like to not use a method such that, say, reaching a planet is comparable to a nuke going off. That would not be ideal). Additionally, I'd like to get, if possible, an indication of how advanced, a civilization with that kind of technology would be. What would their Kardashev rating be? What other tech would they have and how would it affect their culture? etc.
*By "convenient," I mean that, for instance, a team of diplomat's could, at the very least, travel about 5000 light years (not in any kind of suspended animation), work out the beginnings of relations with an alien species, and return to Earth, as the alien society facilitating the travel in this story has deemed methods such as generation ships unethical and, for the sake of diplomatic relations, would like as many of their human guests to return to Earth alive as possible.