Multi-Tenant SaaS: Which Architecture Would You Choose? [D]

NOTE -> I expect answer from people who actually have experience and strong understanding of these. please give something beneficial. I'm building a SaaS platform in Sri Lanka that handles documents and other sensitive data. Each user can upload their own documents and information, and the platform uses RAG to answer questions based on that user's data. That part makes sense to me. My main concern is what happens when the user hasn't uploaded enough information. I still want the LLM to provide accurate answers using reliable information from the internet (or from a curated knowledge base), wit