Which one? https://github.com/Ladybug-Memory/pgembed or https://github.com/faokunega/pg-embed ?
Both will either download or ship the postgres binary with your app, and run it in a separate process. Pglite is different, it's actually a library (they have stripped some parts of the postgres source code) and it could in principle be ported to be used as a native library (meaning, you link to it and run as a single program)
There's even a draft PR to do this, but it became stale
https://github.com/electric-sql/pglite/pull/842
Right now what exists is, grabbing the pglite wasm and running it on native code on wasi
frick this gotta be the tenth time ive read about pglite here and i always go look for native library. shame pr became stale, webapps simply arent always my end game. thanks for putting pglite-oxide on my radar tho, this is an interesting almost-there i can tinker with.