With an offensive rating of 127 and a PER of 23.9. Both of which are the best on our team. Although just barely, Gobert is at 124 offensive rating and 20.9 PER.
Exum's PER would be 9th in the NBA if he qualified. Exum's Offensive rating would be #2 in the league.
Those are according to basketball reference. NBA.com are different. Here are the Jazz advanced stats on NBA.com. Exum is leading in just about everything (besides the 1/2 minute of play from Naz)
http://stats.nba.com/players/advanced/?sort=OFF_RATING&dir=-1&Season=2017-18&SeasonType=Regular Season&TeamID=1610612762
NBA.com advanced defensive stats show great things as well.
Those numbers are probably not sustainable but I think it shows how good he has looked in his limited numbers so far.