Looking at individual player on/off court team efficiency numbers because they're so easy to get for NBA, at basketball-reference.com.
Draymond Green is going to get the max. Warriors are +0.080 PPP on offense with him on court vs. off court, opponents are -0.067 PPP on offense, total margin +0.147. Hometown Pistons are going to throw it at him and let Monroe walk without a second thought. At least 3 other teams will do it too. Just a matter of whether the Warriors want to match. He may struggle shooting when Reggie Jackson and KCP are the backcourt threats rather than Curry and Thompson, but his impact is too great not to give him the max.
Curry should win MVP, though Harden will probably get it because defense is still so undervalued. If it wasn't clear from all the other stuff, Curry's on/off numbers are the best among all candidates, including Lebron, who is putting up monster analytics numbers as usual, and Anthony Davis, whose offense still has a lot of room to grow. Harden's terrible defensive impact is not a myth. Davis has a massively underrated sub who is putting up really good numbers, Alexis Ajinca (20.4 PER), and this hurts Davis here.
Curry: Warriors offense +0.136 PPP, opponents offense -0.026 PPP, total margin +0.162 PPP
Lebron: Cavs offense +0.110 PPP, opponents offense -0.041 PPP, total margin +0.151 PPP
Davis: Pelicans offense +0.068 PPP, opponents offense -0.038 PPP, total margin +0.107 PPP
Harden: Rockets offense +0.135 PPP, opponents offense +0.041 PPP, total margin +0.094 PPP
Westbrook isn't in this ballpark. His defensive impact has been nearly as bad as Harden's, and his offensive impact is much worse. He's not worth looking at.
Lillard's defensive impact is slightly worse than Harden's. Irving is still a defensive liability but he's not in the same ballpark as Harden or Lillard this season. Irving's numbers are +0.096, +0.023, +0.074.
The entire Clippers starting lineup puts up ridiculously impressive numbers here, partially because their bench is so terrible. I believe Chris Paul has the highest on/off total margin in the NBA. Paul's numbers are +0.195 (absurd), +0.005, +0.190. Redick is apparently an excellent defender now. Redick's numbers are +0.090, -0.035, +0.125, which I guess means Redick is more valuable than Anthony Davis.
As for defensive POY, Kawhi Leonard is indeed incredible on defense, but not as good as Draymond Green this season. Leonard's numbers are +0.053, -0.055, +0.109. I believe the best defensive number belongs to Rudy Gobert, at -0.087.