Yes it's going to get a bit confusing because it differs by region. For example on play-asia they have multiple region versions of the games and you can see that the European/USA one is not a key card whereas the Japan/Asia versions are.

Also some sites like Play-Asia are using a "preliminary picture" which doesn't include the key card disclaimer on some titles. Which could wrongly make you think it comes on a cartridge, ofc this should be cleared up closer to release date.

Here is the information I can find at this time based on various retailers in different regions for third party games. First Party Games so far are all on cartridge so nothing to worry about there. The only game that differs by region at the moment is Daemon X Machina, so if a game is on a key card in Japan it will probably be in the west too, but not confirmed.

Elden Ring may not be a key card in Japan as play-asia say it is, but also still only have preliminary box art without the disclaimer and capcoms response is they have no information to share at this time. So that's why I've put a "?" after that.

Guess that's why physical games costs 10eur more in Europe, to absorb the Switch 2 cartridge tax.

EDIT: NVM, it's just an outlier.

As they are not on cart If you buy Hitman, Split Fiction and Streetfighter 6 you will have to download about 180gb onto your Switch 2. Considering you will likely only get about 220-230gb of the 256gb internal to use for games you'll be left with just 40-50gb free space after those three games.

Hitman - 59.6gb 
Split Fiction - 73gb
Street Fighter 6 - 48.8gb

Third Party being mostly on key cards and being way larger in file size than first party games too is going to be a pain in the ass.

Just out of curiosity what does a 2TB compatible Switch 2, MicroSD express card cost?

Because the 256gb cards Nintendo is selling seem too small (their what? 72$ for 256gb?).
Like what does a 1TB or 2TB card cost?

*edit:
https://www.reddit.com/r/NintendoSwitch/comments/1jsbyz3/lexar_ships_the_worlds_first_1tb_microsd_express/

Thats from like 20days ago.

Seems like 1TB is the highest so far.

Edit2:
Found the 1TB card on pricerunner.dk, its going for 2565 dkk (~385$ USD) (probably 25-30% cheaper in the US)
Still that's alot to pay for some more storage.

For comparisons sake, I checked prices on 2TB SSD's for the PS5, and they go for like 900 dkk ( ~135$ USD).
The MicroSD express cards are way more pricey for the storage they offer.

I believe the 256gb was $60 before they adjusted the accessory prices and it's now $65.

I can only find 256gb in stock anywhere and LEXAR is the only brand I've found that has larger products. Price History seems to suggest the 1TB Lexar Play Pro cards were $199 RRP on Amazon US. So yeah these things are expensive. They weren't really a product consumers were buying before.

199$ on amazon in the US, is way cheaper than their cost in Denmark.
Its going for 2565 dkk (~385$ USD) here (on pricerunner, a site that checks shops and lists items according to price).

I completely understand and respect that decision. And I agree: the Game-Key Card is a waste of time -- a sort of half measure that makes neither physical nor digital fans fully satisfied.

But, personally, I just really want to play Capcom and Sega games. After Nintendo, Capcom is probably the best, most consistent publisher out there right now. And Atlus is indispensable in the RPG space.

Game-Key card still has some benefits of physical. It can be traded/sold/rented/lent, you do actually own something that has a value when you buy it.

The downside is obviously that you have to wait to download, it takes up storage space and it's possible one day in the far future the servers will be turned off and it'll be useless.

Game-key cards will certainly help me to save money as I'll be buying fewer games.

This predictable behavior of third parties to avoid physical games is why I don't expect much of a positive effect on Switch 2 hardware sales despite Switch 2 being poised to get many more big name IP games than Switch 1 did.