I agree it's hard to get it to output things in different styles... I started doing a side project for writing with LLMs (ailivrum.com -- my main focus being doing some writing/reading for my younger daughter right now, although I'm structuring for others to use it too).

So far what I found is that doing prompt engineering does not yield great results. LLMs just go with their own style regardless and I had not much luck changing it... it can do some interesting stories though, but it's far from just outline + prompt > gen story to get something that's readable (on the good side, there are many LLMs, so testing a different provider may give better results).