@stoptheflop
I also watched all the games and I was surprised when he played PG because he obviously was projected to play SG in college. I will guess that Coach Self saw in practice how good he was and decided to have him run the point; a real luxury to have a capable 6'-5" PG.
He was extremely good against competition that in some games was the equivalent of a JuCo team but other times was very good and he was rightly named the Tournament MVP. No doubt he is the best combo guard of his class.
KU has had several players (in recent years) that were ready to start and contribute very early on, McLemore, Selden Jackson. Wiggins come to mind and others did not start right away but did as the season went on, Embiid, Oubre come to mind and others such as Perry, Mason and Graham that you could see their potential became outstanding players but not necessarily from the get go.
From what I have seen, Grimes might be the player most ready to start and contribute from day one in recent years; Coach Self has pretty much said the same thing. You mentioned that at the U18 his 3 point shot was not as good as expected but he was shooting from FIBA range which is farther out than college; I expect him to be a 40% or better 3 point shooter, he was at that level his junior and senior HS years and with the additional training I am sure he will be up there in college. More concerning is his FT shooting since he has averaged around 64% which is low for someone that will be shooting fa air number of them.