These screenshots give more information than the HSiFS ones, so I guess it's time to speculate wildly about gameplay mechanics. It's kind of pointless since ZUN will probably change a lot of things, and most of it will be clear after the game releases. But it's fun, so whatever.
Well, for starters, it seems like getting 5 animal items triggers a hyper. Getting mostly red wolf items triggers the wolf mode, and for Reimu, it seems like it's based on the focused shot. And the screenshot with the eagle mode seems like it's based on the Marisa's unfocused laser shot. My guess is that all characters have three unique hyper modes, so presumably Reimu's eagle mode shot would be based on homing amulets, and Marisa's wolf mode shot would be based on magic missiles. Then the otter mode would revolve around the bomb, but I'm not sure how that would work. It could just have an attack that's based on the bomb, or it could be something like a shield that gives you a free bomb when you get hit. I'm not sure what ZUN would come up with.
It also seems like you can use power items and point items as substitutes for animal items. Presumably, power items substitute for wolf items, and point items substitute for eagle items, since that makes the most sense colorwise. I'm guessing the basic idea is like DDC where you have to autocollect a lot of items at once. Then you can use them to charge your hyper, and whether it's counts as red items or blue items depends on the exact counts of the items you collect. I also noticed that in the first gameplay screenshot, there's actually a lot of items. There usually aren't any enemies that drop that many items in the early game, so I'm guessing that killing enemies with one of these hypers will increase the number of items that get dropped. If I'm correct so far, that means there might be some hyper recharge shenanigans where you kill lots of enemies as your hyper runs out and then autocollect the items to get to your next hyper faster. HSiFS was more of a bullet cancelling game, and LoLK was more of grazing game, so it would make sense for this game to be more an item collection based game or something else.
It also seems like the point item value in this game isn't tied to just grazing, so hypers probably also increase the PIV somehow. Different modes probably have different effects, but I can't predict anything at this point. I wonder how the rest of the scoring system fits around this. Reimu's, Marisa's, and Youmu's bombs aren't made to bombgraze with, and I don't think think they're that good for cancelling bullets either, so maybe bombs in scoreruns are mostly for autocollecting and killing enemies. That would also mean that scoring during bosses would probably involve manual grazing, spell card bonuses, and/or routing hypers at particular moments. Spell card bonuses were pretty low in the last two games, so it wouldn't surprise me if ZUN made them higher in this game, especially if boss milking is less prominent. Having said all that, I personally think ZUN would come up with something different for boss scoring. I just don't know what it would be.
It seems life pieces are back. From the screenshots, it doesn't look there's any mechanics in the stages that gives life pieces unless ZUN just didn't use them. There is one bomb piece, but that's probably dropped by the midboss. If ZUN doesn't change the life piece situation, there might not be many lives in this game. ZUN changing things seems like the most likely case to me, though.
I wonder how much of this I got right.