8 app modules? That's a little clumsy. Something that would require that many app modules would be like
docs.google.com and
drive.google.com. Google has a LOT of different platforms which, if programmed in Django, would need several app modules. I'm 90% sure you'll only need one app.
Hardware requirement is not something you need to consider based off Django. It's more about the transaction costs (writes and reads and etc.). Since it's only 30 clients, I imagine self hosting wouldn't be a problem at all. You could probably buy a Raspberry Pi 4 and host on there without a problem for the next 5 years.
Several users logging into the system isn't a problem. Django has session authentication, so users can do whatever they want, concurrently. If you're looking into setting up a Chatroom package, you can check out python's asyncio and django-channels package for asynchronous tasks.
Again, hardware with the conditions you listed should be the least of your worries. Just make sure that everything works and is secure. You could utilize Django-registration and Django-pwned-passwords. Make sure your setting's important information, like the secret key and database passwords, are stored in environment variables.