Can't really say anything on McCoshen, but here's what I have on Bowey:
Madison Bowey - Kelowna Rockets - RD - 6'1 - 194 - Bowey is a big, strong skating two-way defenceman from the D factory in Kelowna. Makes a good outlet pass, skates well for his size and has a very hard shot. I still see him as being pretty raw, but he's athletic and has a ton of skills to mold. Would like to see some solid improvement in his hockey sense, but he's another one of those kids I didn't have a chance to see live this year. I know that many people like him more than I do and that there would be some NHL teams that rank him as a top 25 player. For now, I have him in the 45th overall range on my own board.
I guess McCoshen is the best out of the listed players. big two way defenseman. very complete player, no aspect in the game where he needs to improve drastically. he may not have sky high upside, but he is a safe pick.
Bowey had a good WJC-18, but he is smaller, less physical and has less hockey sense. I would rate him as a mid second rounder, but there are people out there who have him as a late first/early second pick.
Hägg was very inconsistent this season and very bad at the WJC-18. He could still go in the first round because of his upside, but if I have the choice between him and McCoshen, I go with the later.
I am not a fan of Thompson. Do not have him in my Top 60. I really do not know what people see in him to justify him as a early second rounder or even as a first rounder. He brings close to zero offense and his defensive play is good, but nothing really special IMO.