This might be an unpopular opinion here, since the consensus is that he's been pretty poor, but I think Root makes a better test captain than Kohli. I think Kohli's too volatile to be honest. Constant chopping and changing just doesn't help his team's situation whatsoever, and I think this has played a very significant role in the team's downfall thus far.
I think something has to be said about the negative aspect of his intensity as well. I don't think it works particularly well in conjunction with the nature of his team. I get the impression that his teammates, who are already never really assured of their place in the starting XI, are being forced to play at a certain level of intensity that is unfamiliar to them, and as an expected standard of their performance. Pujara is the best example I can think of. I think it was in SA where Kohli commented on his intent, and then his runout problem escalated. In reality, in an era where test matches are regularly finishing with a couple of days left to play, Pujara didn't really have to change. He averages 50 afterall ffs. Not everyone performs at their best when trying to be 'fired up' and dominate the opposition in all faucets. It can be overbearing, and in the case of Pujara, he has been a shadow of his former self.
Of course, the flip side is that Kohli's own performances have elevated as captain. At best, you could say Root has stagnated. But in terms of pure team management skills and tactics I think Root has been more successful.