Thanks for that milk powder chowder recipe (although canned clams may be difficult - canned fish is being rationed heavily in my part of London, that’s if you can even find it)

Nori. All I can tell you is that there are different kinds with one type that disintegrates when wet (which is great for adding to pasta and stirring into dishes) and the other that is sturdier and more robust which is much handier for spam musubi or temaki etc... What I can’t tell you is how to tell them apart without trying it, especially if relying on English packaging or a product information sticker.
There’s also the “Korean” kind (popular in Japan at breakfast time) which has oils and seasonings. These are much more likely to fall apart than not.
All I can say is, check the ingredients. If there is oil listed, or more ingredients than simply nori or laver, I’d assume it would fall apart easily.