I don't rate Dubois as highly as many do if I'm honest. He carries dangerous power but I feel he's a limited boxer. He had Joshua hurt early on, and a very wobbly Joshua was able to evade him for a good few rounds until he foolishly got sucked in and tried to engage.
Parker with his chin, experience and hand speed could get in close quarters and cause all kinds of problems. Dubois is not known to fight on the back foot, as with close quarter shorter types, the game plan would tend to be to fight on the back foot, keep some distance with your jab and catch the shorter man as he gets desperate and tries to force his way in.
You never truly know with boxing though, so hard to judge fighters who have never been on with each other.
If I were Parker though, I'm not taking this fight. I was due a championship fight and now I'm up against someone arguably more dangerous and with no title on the line.