If you are worried that 256GB of UFS storage is too small, remember that the Switch 1 only had 32GB of storage. The actual usable size was 25GB.

And the file size of the games in 2017,

Mario Kart 8DX is 11.3GB.
Breath of the Wild is 13.4GB.
Mario Odyssey is 5.7GB.
Splatoon 2 is 5.5GB.
Xenoblade 2 is 13.1GB.

It could only fit 2-4 games inside and most of the player just bought SD cards to cope.
Meanwhile, the console was selling like hotcakes for years.

Doesn't the ps5 require M2 storage?  Or do you move files around?  

Sure, but 3rd party support was soft.  And the question is will 3rd party put full games on the carts?  If third party games require significant downloads that 256 gb will be eaten up quickly.

But yes, expandable storage is the key.  I'm not saying 256 gb is a problem, but it is small and will require some sort of S2 storage upgrade.  

I thought that was the point of SD Express?

It is, lol. 

The 256GB on board storage just has to be large enough for any single game.

SD Express cards from Samsung (800MB/sec) are coming this year, although really there's nothing stopping anyone from storing just using bog standard current SD Cards. People have tested this stuff on Steam Deck, using even old SD Cards work fine. 

If you're downloading like a large game such as Call of Duty or say a Final Fantasy VII Rebirth type of game, I would keep that on the main internal storage, and then just have a SD Card in the 256GB-1 TB range depending on how many games you feel you need to be able to play at one time. 

I'll be picking up probably a 512GB Samsung SD Express card when I get my Switch 2, that's 700+ GB of storage, very high speed internally, high speed enough even off the SD Card itself. 

I'll be picking up the 256 SD Express before Switch 2 launches but I would like an idea of the pricing. Are we talking 1TB SD pricing like for my Series X? Any idea on how much that 512 will cost for SD Express?

Samsung released UFS higher speed memory cards like in 2016 but no one ended up using them (lol), but those cards even years ago were like $59.99 for 256GB:

https://www.samsung.com/us/computing/memory-storage/memory-cards/mb-fa256g-am-mb-fa256g-am/

Maybe you'll be able to get 512GB for $60-$70 given it's 2024 now. 

I saw that actually I just don't understand what those are compared to SD Express. I understand UFS 3 is what Nintendo could be using internally but are those UFS cards the same tech but in micro? I'm no tech person, so I don't understand.

It's just an example, those are 500MB/sec cards. I got the feeling from Samsung's press release that their cards are basically going to be about the same price as regular SD Cards. 

The tech for faster SD Cards has been around for ages, the thing was no one really wanted that much speed so now SD Card makers bothered with higher speed cards. It's not really a matter of the tech itself being like bleeding edge expensive or something. 

SD Express is 800 mb/s. Should be plenty fast for games, loading will be longer than ps5 at 7,000 mb/s but going from 2 seconds to 12 seconds, no impact.

The S2 will need user upgraded storage, but to be fair the same is true for the ps5 and Xbox.