Higher numbers are theoretically better, but the numbers don't mean much.
The rookies are actually real players in the sim database. You can search for them in the player search. Use their per%, mid%, pnt%, and position effectiveness and use a range. So, if your rookie is 80% effective at PG, 90% effective at SG, 100% effective at SF and PF, and 90% effective at C, search for 79-81, 89-91, 100, 100, 89-91.