@SB5416 The Azure OpenAI on your data official doc would be your one stop shop to start building what you are looking for.
You wouldn't really need separate instances of OpenAI as such since the context coming from Azure Cognitive Search (which provides semantic search) has document-level access control built-in, allowing users access to context only specific to them or their role.
With Power Virtual Agents, you can quickly get a teams bot up and running with little effort.
But if you specifically require a custom web app, the sample web app mentioned in the doc would be the perfect starter to build your own. It comes with the following functionality you could use directly or use as reference for your own implementation
- Chat History (logging)
- User Authentication