Thank you @crackaddict for the elaborate response. A deeper sidecut will make the waist width smaller and that's something I did not think about, or did not know how much it actually affects the width.
I am asian myself and even amongst asians, my feet are incredibly small at size 7. So i guess I am lucky not having to downsize on boots . I think I will look for some board within 255-260mm to begin with because a larger sidecut may be harder to control at my current skill level.