First MLB at bat is a walk.
People love the power/speed combo with him but the on base skills is what is going to make him stick in the majors soon. 124 K's in 405 ABs at High A and Double A is a little high (30%), he probably needs to get the Ks closer to 20% if he wants to be a leadoff hitter (which is his ideal spot in the order IMO). But even with a highish K rate, he also drew 72 walks at those two stops which is pretty impressive. He only played 61 games at high A, yet drew 45 walks which still has him in the top 20 in that league in walks.
Had he had enough bats to qualify, he would be leading the Carolina League in OPS and would be third in the Eastern League. Neither of those leagues are known as hitter leagues, so add in the speed and you have the makings of a premier player. Very Byron Buxton esque, although we have seen how Buxton has worked out thus far. I think they are about the same player though, hard to imagine either failing long-term. Not sure Moncada will be an elite base stealer though, but I can see him being a guy in the 30s with 40s upside. Buxton probably a 50+ steal upside, but Moncada is going to have more power.