How-To Question: Best Practices for Setting Up a Multi-Brand Help Center?

We're in the process of setting up a multi-brand Help Center for our two distinct product lines. We want to ensure that the customer experience is seamless and that each brand's identity is clearly represented. What are the best practices for structuring the content and categories for a multi-brand setup? Should we create separate top-level categories for each brand, or is there a more elegant way to handle this? We're also curious about how to manage user permissions and agent access across the different brands. Any advice or examples from others who have gone through this process would be incredibly helpful. We want to avoid common pitfalls and get this right from the start.