There is no such thing as soft canon here. Either it exists or it doesn't.

It's not like, say Kingdom Hearts with its novellas and manga. Is it 1.0? Then it's canon. Is it a side quest? It's canon. Is it a minion description? It's canon.

Did I player theorize that something is possible because of circumstance X Y and Z? It's not canon.

BUT!

That's the point of RP. To play a role. And you can always find someone down to share your ideas.