That's what google scholar is for. Use it to find the meta analysis papers and go from there.
Which incidentally shows why RAG just means vector store + embedding model, since your definition means different things to different people and an implementation can't exist until we figure out AGI.
For alternatives to vector search, see GraphRAG and AST parsing; e.g., https://vxrl.medium.com/enhancing-llm-code-generation-with-r... or https://github.com/sankalp1999/code_qa