@MDScheitlin: I’m not sure how that would solve this problem. It would essentially just amount to a nested vault, wouldn’t it? (I might miss something though.)
To give at least a partial response to your question, @ajgxyz: The (hidden) .obsidian folder within every vault contains everything related to Obsidian’s configuration for that vault. So, for instance, hotkeys.json contains your hotkey settings, workspaces.json contains your saved workspaces, etc. The plugins, themes, and snippets folders contain, well, just that.
So if you wanted to keep your configuration exactly the same, as far as I’m aware you’re essentially looking for a way to keep all the contents of the respective .obsidian folders in sync. Apart from simple copying and replacing, you could probably achieve that with a tool like FreeFileSync. But I’ll leave it to others to point out (and am myself curious about) the clever and elegant ways to do it 