Boldy, to me, is a two way forward who looks like he could put up 30g+40a, be a stud penalty killer, and a leader. He isn't overly physical but knows how to play the body and use that big frame to his advantage. He probably shouldn't be the best player on your team, but if you have a good enough team, he will be the reason you win the Cup. Basically, he is everything Coyle is, was supposed to be, and more. He is independent enough that I don't think his development will be ruined no matter what team he goes to. He'll just be successful. I read a comparison earlier today to Patrice Bergeron - I wouldn't go that far, but I definitely like the guy.
Kaliyev is that top line winger who scores 40+ goals - while also being liable for nearly just as many over the course of the season. He will be the guy you throw out in dying minutes, hoping that he scores to tie it up or win it. And he just may do that, but probably as often he'll be out of position and a scoring chance will go the other way. If he's the best player on your team you're probably in trouble, but if he was playing with a guy like Granlund - you'd have a top-5 line in the NHL. I think a lot of his success will depend on where he goes and who he plays with.
Caufield is a bit in the middle of them. I don't think he'll score as many as Kaliyev - but he won't be the reason you lose games, either. I like him a lot - DeBrincat 2.0 if things go well. He will depend on his teammates a lot - I don't think he'll be the driver of offense - but he will make things happen.