I attempted this last week. It's easier to redirect them. So category.forum.com redirects to forum.com/category/2
I pasted my configuration in another topic. Feel free to look through my topics from the last 2 weeks for one about subdomains
You can hide composer (red button with +) and chat (user avatar as a button) windows by clicking on their respective buttons in the bottom right corner of the screen. Click again to show window and see your own content.
Try to browse forums when composer is opened. This is one more possible action to do.
@vij You might want to reach out to email@example.com
I don't know their plugin pricing but those features don't sound like too much effort. And if you allow it to be licensed at their will (please be more precise on this, "sell them to others" might be more restrictive than you want to be) it might give you bonus points
I myself don't have much spare time right now, so I'm out of this.