A lot to unwrap here, which llm are you trying to choose for what?
The CDCK LLMs are only available for very specific features, to see which you need to head to /admin/whats-new on your instance and click “only show experimental features”, you will need to enable them to unlock the CDCK LLM on specific features.
Any LLM you define outside of CDCK LLMs is available to all features.