Johnson has changed, his finishing and arrival at far post for tap in has absolutely be an improvement since arrival. 10 goals before mid season is a significant uplift on his game.
Always hard to determine the difference between coaching and player settling into system but Johnson, Dragusin, Sarr (adding goal threat), Deki (in central role), Porro (before his legs went from overplaying) are all easy examples of players who have improved under Ange.
Re Djed, hard to understand from outside but his challenges have never been talent and Ange isn't the only manager who has sidelined him.