Sorry I am not that knowledgeable about these things. By another registry, do you mean use another docker account? Or by "registry Auth" do you mean to add runpod creds? Or something else
Registry Auth is in runpod settings, it's docker username + docker api key it helps if your speed is probably throttled by ip (runpod shares ip on some machine) Feel free to search things up too
Another registry means like aws ecr, gcp container registry or from github container registry or even self hosting your own But so far I think best one is dockerhub