My house is set up like this. I have separate entrances for both units but they share a common entryway.
I lived downstairs while i was renovating and rented the upstairs. It gives you a pretty good perspective on noise levels living downstairs while renting upstairs.
Now I have moved upstairs. I did add extra insulation to the ceiling in the bathroom and insulation in the ceiling in the hallway.
Thick carpet and pad is good for the bedrooms rooms and entryway stairs (it absorbs sound-the thicker the better).
I remove my shoes upon entry upstairs and I’m mindful of my footsteps when walking around.