For what it is worth, it is hard to foresee Obi Toppin dropping to the eighth overall pick on draft night. That said, it is really hard to predict a team that would be willing to take him based on what they already have. Many teams above this spot already have young power forwards in place, defensive woes in the frontcourt, or not enough complimentary basketball players.
The Bulls already have Lauri Markkanen, yes, however his overall development has been flat overall. Pairing Toppin with Wendell Carter in the starting backcourt (with giving Markkanen a sixth-or-seventh-man role could benefit all parties. Toppin is a great three-level scorer that has a good shot and works in the post. He can also facilitate some, although he is more of a complimentary playmaker than a primary one.
Toppin could be a very good pro, but he is 21-years old, two years older than most of these players. I am willing to bet on his shooting and athleticism translating to the NBA, though.