After watching a few full games of Doncic, I will say that he has better court vision and passing than Fox. Fox has the better handles.
Luka also seems to be more effective when he initiates the offense, so he is surveying the defense when he has the ball. If Luka was the initiator on offense, you would need to use Fox more off the ball. I think Fox is more of a score first point guard anyways.
With Doncic handling Point Forward and Fox as the Scoring Point Guard duties, I would start Buddy at SG to give us a knock down 3 point shooter. Bogdan would be the primary ball handler on the second unit. With Giles and his (rumored and hyped) passing from the PF position, I can see the ball movement being excellent on the Kings next year!
PF: Giles / Skal / ZBo
SF: Doncic / JJ / Temple or Jakar?
C: WCS / KK
SG: Buddy / Bogdan / Shumpert
PG: Fox / Mason
The Kings would be sure fun to watch!