This is cool.

I started to look at the wasm stuff, but all the documentation I found was so high-level as to be meaningless.

What do you recommend for someone who would want to be able to create or read .wasm files?

I'd say jump straight to the specification (maybe v2, which is simpler).

But I occasionally saw one or two articles around where they explain how the binary format works, which could be a good introduction before jumping to the spec.