I think I played enough of the game to give some first thoughs.
Toad Scramble
If you followed this game at all you already know how it plays, the question is: does it work? In my opinion, yes.
One thing I really noticed is that this mode puts a lot of emphasis on the freedom of the player, you can go anywhere anytime you want, there is no time limit on when someone has to reach the boss and how you play is all up to you. This does work well since coins and the partners you can recruit are far more important than one might think, it's easy to think that rushing to the bosses as quickly as possible is an advantage, but that's really only the case at the beginning (and even then not always) since the partners do help in boss battles and once they become more numerous you'll be havin' a much harder time if you are all alone and you do get a star per 10 coins at the very end, so you do have to keep everything in mind, while maintaining full control of your progression at all times.
Minigames occur when players collect coin balloons that are put on certain places of the board or in matches that allow a player to take a partner away from one opponent should they win, which ultimatly means that they come up fewer then in the traditional style, but in this case I do feel that the board gameplay itself is engaging enough on it's own to make up for it, thanks to the fast pace and bigger focus on strategy, especially with items and item shops coming back.
I haven't played all of the boards yet, there are 5 worlds with 3 levels each, all longer and with more traps, I played one of each, with the sole exeption being Bowser's Castle, where I played all three levels, the final being my favorite board so far, since it is huge and has a lot going on.
Coinathlon
In this mode you collect coins in three out of twelve special minigames to have your character race to the goal (one space per coin), you can earn items that you can use to attack your opponents, when optaining enough money and it is also possible to get combos when collecting many coins in quick succesion, which gives you items quicker.
There are three lenghts for the race: 3,5 and 7 laps, when playing the latter two Bowser will show up at the halfway point and initiate a Bowser Minigame, which is all about survival, those who lose will be send back a couple of spaces.
The idea behind this mode is to find the most effective way to get a lot of coins and react well to the tiems that get thrown your way and I do like it, very hectic and never slowing down for anything.
Balloon Bash
This mode is similar to Toad Scramble, as in you navigate (much simpler) boards, this time with a character of your choice, collect coins and buy stars, with minigames being more frequent here, with one happening almost every round.
It's a nice alternative to Toad Squad, which while simpler in terms of board play, puts minigames more into the spotlight again and is somewhat closer to the old style.
Rhythm Recital
A special rhythm minigame where you play an instrument along to several classic Mario songs, neat idea in concept, but the execution is pretty shite, it's incredibly dull and the notes you have to play aren't even in tact with the music. Look at any footage of this mode and you'll quickly know what I mean.
Mario Shuffle
Two teams of three character have to make it to the opposite site of a short linear board, you roll two dice and choose character moves according to which dice roll. No depht. No minigames. It's dull.
Those are some of my thoughts on the modes I unlocked and played as of now, there is still the Boo Puzzle Party and Challenge Tower, but I have to unlock those.
As far as the minigames go they are good, they are only free for alls (along with bosses obviously), much like Island Tour, but unlike that game they do a much better job at getting you competetive against the other players, since that game often had everyone seperated as opposed to having a direct fight against each other. i also like how not all of the boss games are direct fights, like the Blooper one, where you have to hit a ball in the rhythm that the Blooper is conducting, it's actually quite humerous to see.
So yeah, I'm writing a bit disjointed here (blame me being tired), but the point is that my impressions so far are positive, the two modes that I don't like are clearly afterthoughts, while the three main modes do deliver in my opinion, althought there is still more to play, so I'll see if my opinions change.