Answer 8 key questions: should the task run on a fixed process or dynamic decisions, and does it need proprietary knowledge — then pick Prompt, Workflow, RAG, Agent, or a combination.
First judge whether the process is a fixed path or needs to decide its next step from intermediate feedback. Then judge whether the answer depends on proprietary or frequently updated material. The first decides the execution-control style; the second decides whether you need RAG.
Background only shapes the implementation tips on the result page, not the architecture judgment itself.