Yamamoto commands all of his pitches well and has incredible walk rates in Japan. He has an athletic delivery and should continue to have plus command and control in MLB. The balls used in MLB are different than in the NPB and this often leads to Japanese pitchers losing a bit of command and control when they come over to MLB especially early on. There is no easy way to evaluate command statistically but there is for control. Here's a table with the BB/9 (walks per 9 innings) of some of the major Japanese pitchers to come over. Only full seasons are included.
NPB Posting Year BB/9
MLB Debut Year BB/9
NPB Career BB/9
MLB Career BB/9
Every case is different and there's a lot of factors at play here for each pitcher. That being said, it's very likely that Yamamoto will not maintain his 1.5 BB/9 this year in MLB. It would be safe to project around a 2.3 BB/9 in his MLB debut season before he stabilizes around a 2.1 BB/9 which would be in line with his NPB average and still be around the 90th percentile in MLB.
When coming from a league in a dead-ball era with a different schedule, different ball, no shift restrictions, and far worse power hitters it would be foolish to ignore that there's risk here. Yamamoto certainly has good stuff but Senga, Darvish, Kikuchi, Ohtani, and Imanaga all struck out more batters in their respective posting years. Pitchers can succeed in a variety of ways but something like contact management has not proven to be as predictable of a translation to MLB as strikeouts and a lot of Yamamoto's game is about keeping the ball on the ground and in the park. This sounds like a pessimistic outlook for an obviously incredibly talented pitcher but it's all in the perspective of his $200M+ price tag. Typically a foreign pitcher comes at a discount and that will not be the case here as you're paying him on the assumption that he is a top pitcher in MLB. Even with likely growing pains next year it would be reasonable to expect him to improve with more experience in the league and eventually become an ace. Given his age and what we know about his pitching ability, giving him around 200 million seems like a fine investment as long as the money does not prohibit filling other pressing needs.
With a likely impending bidding war that will result in Yamamoto being one of the highest paid pitchers in MLB history, this would be a career-defining gamble for Ross Atkins and Mark Shapiro. If it works it could save their jobs down the road and if it fails it is all but assured that someone else will be running baseball operations in the future. Even if there's some industry skepticism regarding him, there's zero doubt that it would be the kind of "big splash" that would bring back a lot of excitement around the franchise and hoist the Blue Jays rotation into best in baseball conversations.