is there a correct way? I got Rome bindings and they said it should be mounted in picture A. Will it mess anything up if i go with B?
The correct way is to get your boots mounted centered across the width of your board (or if you like slight toe or heel bias). Mount it like A, and check it. If you have heel cup adjustments mess with that, along with toe straps.
If you can't get it to work that way, try picture B. I've had a binding where picture A was perfect. I've also tried a binding where pic A had half my boot off the heel side.