First post here, quite new to Obsidian, came here through google search, as I wasn’t sure how to handle what I want to accomplish in terms of vaults. Now I have the answer – thank you guys 
What I got Obsidian for was to build a Zettelkasten specifically. I think Obsidian is perfect because of the robust features like file format, local storage and markdown, while also offering “high tech” features like the graph view and multiple panes. Seriously a dream come true when I found it VS more conventional apps geared to Zettelkasten like Zettlr or The Archive.
What I learned from you guys:
In Obsidian, a Zettelkasten belongs in its own vault.
I know there’s been some hype about ZK method in recent months, but I feel like sometimes people use that term a bit too liberally, ultimately confusing it with a mere note-dump that can be cross-referenced.
Now I absolutely don’t want to tell anybody how to take notes or organize their life, but for a Zettelkasten to be a Zettelkasten only very specific types of notes are taken, and the only notes referenced are other Zettel, period. It’s not a place to integrate with and reference daily journals, projects, videos or whatever else you might have floating around. Only very dense, thought out particles of knowledge/thought.
I don’t want to deter anybody from building a system where all kinds of things go in and can be interconnected. If that makes sense to you, go for it. But that is definitely not a Zettelkasten.
So for me, as I want to follow the ZK “rules” closely: One vault for the ZK, one vault for all the other things I want to throw at Obsidian