I don't think our evaluations of Mikal are terribly far apart, at least on defense, where I see him as a guy who will be a plus team defender and good enough to hold his own against a wide variety of offensive threats, but not a likely all-defensive teamer or defensive anchor. If that's who he is on defense, and he's more of a high-efficiency 3rd/4th option on offense than a potential leading guy, then that's probably not worth a top-10 pick to me, not in this draft.
Comparing Mikal to Jontay is such an apples-to-oranges thing that I'm not sure we'll get anywhere, but I don't think he's nearly reached the limits of his development.
In particular, at an age when most elite players his size are just starting to show flashes of an outside shot, he's a step ahead, showing flashes of ability to shoot off the dribble from deep. That ability would make him a very difficult player to guard; even "skilled" bigs typically are reluctant to put the ball on the floor from the perimeter, and have limited options when they do.
Additionally, at an age when most elite players his size are learning how to make simple, textbook passes to keep the offense moving without turning the ball over, he's again a step ahead, often acting as a focal point in the offense, recognizing that he can use his size to see over the defense, and actively trying to get the ball to guys in advantageous positions rather than simply passing the ball back out to a guard who can reset the offense. Bigs who can reliably orchestrate an efficient offense are still a great rarity in the NBA, and defenses haven't really developed effective countermeasures yet.