For consuming I would use the standard content delivery API.
For creating, I would build a separate custom built web api 2+ using standard .NET that uses the IContentRepository in the background to create the required content.
Then you can call on that api to create your forum posts etc.
Ed, there is currently no remote write API. It is being developed right now, and we're hoping for a January 2021 release.
That's exciting. Looking forward to more information.
We are building out a headless CMS using the Content API. One of our requirements is to create a forum and submit data that will include necessary fields for a particular content type we have configured. Is this possible? Is there a REST API we can hit? Any hint as to how to go about doing this?