Bronny is an excellent defender, he is just small so really can only guard PG. Springer and Thybulle are big enough to guard multiple positions.
Bronny's game is very similar in style and skillet to his father, he just is no where near as big and athletic, which is why he struggles. For as good as Lebron Sr. was, even as a rookie, it took him years to develop a consistent shooting touch and to hone and focus his talent. He was just so lifted athletically he could get by until the skills caught up to the physical gifts. Bronny just doesn't have the same physical gifts his dad has. He has skill and instincts, he needs time to hone them to fit his frame. That is why for years I've said Bryce is the better prospect. He is much closer to their dad physically.