I'm quite confident that you, if running an Asiair at least, don't need to apply any backlash values because the computer will sort it automatically during the AF routine. I don't have a link on hand just now, but the information comes straight from ZWO and their forums. There are backlash settings but I've just figured they were for manual focus, just like the step sizes you can enter, which are also for manual focus. I don't know NINA so I can't speak for how it works there or elsewhere.
I've got two Asiairs and two EAF's and I'm using them with refractors, lenses and an E8HD. I've not touched the backlash settings and it works perfectly as is.