I have watched bits and pieces of a number of his matches over the past year. At present his height gives him a major advantage, particularly on serve, which he uses well. There is plenty of power in his shot making but the rest of his game is erratic, and he has spells of breaking down early in rallies. His game will be put under more scrutiny when his cohort develop physically to be closer in size. You can see for yourself by watching today's final
Yes, I've watched Mark Ceban a couple of times - his matches at Wimbledon this year were streamed, of course, and I caught big chunks of those.
And I saw him playing Les Petits As
As you say, rather gangly, which is unsurprising, given his age and height. And that gangliness causes errors - he doesn't quite know where his feet are sometimes I actually expected him to be more aggressive - I think he's obviously a little caught at times between wanting to use his weapons and being scared of errors. But there's quite a lot to like there - you say his game will be put under more scrutiny as the others grow but there's also the other side that a lot of smaller, more consistent juniors do remarkably well but players like Mark actually really come into their own when they get a bit more muscle on their frame and learn to control their limbs.