the black bars on the top and bottom of the screen are baked into the renders (before the mega UI revamp, those bars were used as the "box" for the dialogue and menu, hence why they existed)
there is no way of adjusting them, as explained above
but don't worry, those black bars will disappear in the future (maybe), probably at a time when beta begins.
also act 3 content (late game), do not have black bars baked into them