On the second point, Obsidian’s vaults are intentionally stored as a single folder that can be synced easily, including all settings. They do have a service for syncing, but with a bit of tech know-how it’s still really easy to sync. Also, all notes are stored as plaintext markdown files, which is convenient since many programs can read markdown.
Rest is correct tho.
Yes and yes. The folder is just a bunch of markdown documents, as well as a hidden folder containing configuration, plugins, etc (json, js, css, etc). The vault is entirely self-contained.