When using the free version or the Personal PRO versions of Collabwriting, all topics are private by default, but you have the option to share them when needed.
You can set these preferences for the whole link or add individual guests.
Learn more about sharing options here.
On the other hand, when using a team workspace, team members can see all created topics by default.
If you want to keep some of the information private or share it with a select few, you can create a private cluster.