"How would you say real life BDSM/kink varies from fantasy BDSM/kink?"
Well, I think most people fantasize about stuff they were never do in real life, and I do that, too. And I think fantasy BDSM always goes smoother--and probably kinkier--than real life BDSM.
In fantasy BDSM, the people are always hot and bothered and expert at doing exactly what needs to be done to drive the other person crazy with need. The rope always twists the way it's supposed to, the knots always hold, and the lube never spills.
In real life, of course, scenes usually don't go so perfectly. The leather hits the wrong bit of skin. A limb twists the wrong way, and needs a second to recover. A knot gives, leading to a suddenly flailing arm or leg. The sheets get messy. The furniture creaks. Things don't feel the way you expected, things don't work the way you wanted...laughter ensues, when you weren't planning on things getting funny at all.
But that's what happens in real life. If you're lucky, you have someone to share your fantasies with, to indulge them and play them out with you. And sometimes your fantasies don't play out the way you imagined them. Sometimes real life is even better.