A lot of the time, the difference between an NCAA D-I and II player is size. Most D-I guards usually range from 6-foot-2 to 6-5, with an exceptional smaller player often making it on talent and heart.
At D-II, you usually have smaller guards, but some have the talent to make a D-I team and not play much. Some of those players opt to go the D-II route to play.
Most D-I teams have centers in the 6-9 to 7-foot range; the D-II teams 6-7 to 6-9, with an occasional 7-footer. But it's almost guaranteed that if you're 7-foot and can play at D-I, you're going to be at D-I.
Same goes for forwards. In D-I, range often goes 6-6 to 6-9 while in D-II it runs 6-4 to 6-7.
Malik Johnson, Deforrest Buckner and Patrick Matthews have solid size that will give them a chance at the next level. What level they'll play will depend on how much they improve their all-around games and strength in the coming years.
Right now, because of their age, Johnson and Buckner have a good upside with two years to get better. Both should have some type of college offers when they finish, but they've got to really improve their perimeter games to have a chance to play D-I. At 6-6, neither could play in the post at D-I. That means, playing a 3 and maybe a 4. Same thing at the D-II level; or maybe playing inside at D-III.
Matthews is better on the perimeter with solid ballhandling skills. Like I said above, he needs to get into the right program under a good coach where he can continue to develop. He's got a good shot at D-II, but D-I is a long shot.
I like what former Iolani star Kyle Pape did, attending D-II School of Mines in Colorado. He had some D-I interest, but chose the Colorado school because it was a good engineering school. It also allowed him to play a lot rather than go to a D-I program where he might have sat the bench most of his career.
Kyle had an outstanding career at the small Colorado school, being an all-conference player, and got a great education. A win-win situation.
Good luck to Malik, Deforrest and Patrick this year. Keep working hard on your all-around games. Being able to play inside or out, handle the ball and shoot it pretty well from at least mid-range will improve your stock for college.