The distribution of perimeter and inside shot attempts is supposedly roughly related to the ratio of your player's LP/PER ratings. In other words, a 90/90 guy set at 0 will take about half outside and half inside shots. The + and - ratings will adjust that as well as the defense you play against. If the defense is set at +3, he may take fewer outside shots. If the defense is a zone, he might take more.
Frankly at 90/90 the guy should be a tough out either way. If he plays against a zone, I might make him a +1. Against a press, maybe -1 to go inside more and draw fouls. Lots of options at that rating level.