The poor girl has been aching to touch people for years. Once she gets her coolant upgrade in act 2, she immediately asks her romantic interest if they can go to bed.
And then, nothing. Her romance appearance during a long rest is queued at the bottom, behind Gale’s advances, Wyll’s quest and even durge’s butler. Then nights pass when nothing happens. Finally, perhaps a week later, the romance resumes. During that interminable delay, Karlach is eerily silent. It is baffling, a clear game error. Karlach needs to be on top.
And on that subject, you would expect the barbarian to be a top. It is a good bit of character depth when you realize when it comes to romance she is timid and shy. That said, I would expect her to be on top by act III.