If you don't want to wait in line for how ever long it is u can buy the vip(priority)ticket,i did this when I went to the Australian comic con(to see William shatner)got to see in less than 10 minutes(I was able to talk to him for a few minutes,i was able to be have priority for autographs and photos over the ones who just brought the normal tickets)It all depends if u want to spend money getting one and which actor you want.my money was well spent that weekend(I also mange to get Robert O'reilly(gowron)and J.G Hertzler(martok) autograph and signed photos.
I can't say about photo op experiences, because I've never paid for such. But I do have photos of myself with actors from before that horrible trend began. So I totally get wanting such. If you have a particular favorite, or two or three? It could be worth it for that. Without having been through that particular procedure though, I can tell you that the bigger a convention is, the more rushed, impersonal, and cattle-call like experience you're going to get. I've been to small cons and big cons. And Vegas is a MEGA con. It's the grand-daddy big-time super-bowl convention. Which means more than likely you'll be lucky to spend 15 seconds with the person, maybe 30 at the outset. Yes, you may get a hand-shake. A "nice to meet you" or something else. But you can sometimes get that from an autograph op too. Really I don't know what to advise you to do other than this: go with your gut.