I'm probably just an idiot cuz I haven't played as many modern Mario games as most people but I love that they made Bowser's Castle/Kingdom like a floating fortress. That actually really hecking works. And, the lava and fire animation is phenomenal. Bowser looks sick. It's his eyes that are mostly different from his standard design, but he has a rather elaborate design so slight tweaks I think work a lot better because overall it's very consistent to his expected look. He's big, he's mean, and so imposing.
Mario has a simpler design so every tweak especially on his facial proportions are going to look more uncanny. I think his head might be too wide, or his face is too small for his head? I'm not actually sure what is making it look off but Luigi translated well.
Environments look pretty good. I will need to see more of the Mushroom Kingdom before I decide how I feel about how plush the mushrooms are, though.. but as of right now I'm not really feeling that.
I actually forgot how much of a presence Jack Black has in animated movies now, people memed about Kung Fu Panda and I'm still like thinking of his role in School of Rock as my main impression of what his performance would be. Glad he worked to fill the role of Bowser with the force behind his voice. It feels in character. I do kind of wish Chris Pratt filled the personality of his character a little better. It kind of sounds identical to every animated movie protagonist's voice, though when he says "Mushroom Kingdom, here we come," there is a hint of personality there, so hopefully we see more of that in the movie.
Toad sounds like a Toad, pretty meme.