The pay wall is only to track points, keys, and link with the app. The only thing meaningful that’s actually locked behind it is the Bowser Jr. mini game. All other mini games, including the ones you get keys from, are playable without it.
This is wrong, but I don't blame you or anyone else for spreading it. Universal and Nintendo do a very poor job at clearly explaining and marketing what exactly the Power-Up Band content actually is, what exactly you need it for, and what you don't. I've genuinely thought of making a Masterthread/post for use as a guide, because I've experienced a lot of SNW myself and there just isn't a ton of accurate info out there on the internet for Epic yet.
For Key Challenge games, Goomba, Koopa, Piranha Plant are all locked behind the band. The Key touchpoint used to start the game cannot be activated without it. They literally will not function without one.
Goomba and Koopa are single-player games. Piranha Plant is a group game. Only one Band is required to play Piranha Plant, but up to 7 other people can join in a game without one. If multiple people in that party of up to 8 players have a Band, they are each able to win a Key.
Bob-omb and Thwomp are playable without the band*, as the Key touchpoint is actually just a big touchscreen that activates for anybody.
*Unless the line is too long and they'll start turning people without bands away there too. Or if the TM just decides to not let people without Bands play.
Bowser Jr. Shadow Showdown requires the Band and 3 Keys from the other games to enter, but only one person in a party needs to hit those requirements. As long as someone has 3 keys on their band, the rest of the party can join. Theoretically, there's no cap to how many people can be in that party. From what I've heard, it's mostly discretionary on the greeter.
The Note Blocks and Coin House games are playable without a Band. (These games are
very simple.)
The Toadstool Cafe Gift Boxes require a Band to activate.
Binoculars are usable without a Band.
None of the collectibles or hidden "M" touchpoints will activate without a Band.
The Power-Up Wall is technically playable without a Band, but will only give out Coins 90% of the time. Bands will activate the actually fun Power-Up minigames 100% of the time.
Punching the "M" Touchpoints underneath blocks won't do much more than play a dull "thud" noise if you don't have a Band. With a Band, they play their respective sound and light up. Same with the Yoshi Egg Block.
I really wish there was a resource for this kinda stuff. It's why I've honestly thought about making one myself. LOTS of misinfo out there, or complete lack of info.