I would look into NovelAI for writing, it’s quite specifically for that. It’s a paid servicd similar to chatgpt, but it’s uncensored and private.
You can run your own lightweight LLM on a laptop but the output will be useless. Good output requires big boy compute.
If you do want to run it on your own hardware, look into Ollama. There’s also options to run your own LLM in the cloud with a not too difficult process for non-techies.
Frankly, id find the right LLM for your needs and just pay for it per month, maybe novelai, maybe something else, but chatgpt is not great for creative fiction.