The 49ers (3-2) took the lead for good shortly after the 15-minute mark at 47-46 and pushed the margin to 10 after the midpoint of the half.
The Panthers (2-3) had a late 6-0 run to close the deficit to three on Brandonn Kamga's basket with 12 seconds left. Luka Vasic missed both free throws for Charlotte with nine seconds left, but Andre Fox missed a 3-point attempt that would have tied it in the final seconds.
Kamga finished with a career-high 26 points and Fox added 10 for High Point.
Charlotte led by as many as 11 in the first half and went into the break with a 38-33 lead. High Point had an 11-3 run early in the second for its only lead at 46-43.
Mannion, who recently reclassified and is ESPN's No.11 overall player in the class of 2019, chose Arizona over Marquette.
He'll fit in with Sean Miller's plans for a faster tempo on offense.
The cream of the crop of American high school basketball will congregate in Colorado Springs from Oct. 5-7, as USA Basketball unveils its newly expanded Junior National Team minicamp in collaboration with the NBA, NCAA and NBPA.