Disagree on one point. It's true that throughout the draft, the NBA drafts kids who have "raw potential." But, in the lottery, nearly every kid, in a good draft class, is a finished product unless the kid is a 7-footer. Last year, Jonathan Isaac had perhaps the thinnest resume in terms of stats, but he was a 7 footer (or near enough). Neither BB nor Walker have anywhere close to the stats needed to be lottery picks. Just off the top of my head these kids are all way ahead of our kids in the 2018 draft class: Doncic, Ayton, Young, Bagley, Bamba, Sexton, Miles Bridges, Williams, Knox, Jackson (I'm not including Michael Porter, arguably a Top 3 pick before his injury).
I know there was at least one mock draft in early December showing Walker going as the last lottery pick and BB as the next pick, but that analyst was giving Walker slack based on the knee injury (no longer as much of an excuse). The same analyst said that BB wasn't that talented. Unless they play considerably better than they have to date -- BB hasn't been bad, just not great -- BB and Walker are going to have to decide if being picked >18th in the Draft is worth it. Walker has the higher ceiling than BB because his shot isn't broken. It also looks like Walker is quicker and a better jumper than BB, but BB has grit and really good defensive instincts.
The rest of your post was spot on.