TL;dr. When it comes to LLMs, there is no “one size fits all” answer to the question “which model is the best” (for NSFW content) because the answer depends on individual preferences, content sought to be written, and elected settings (such as temperature). We are going to do our best to give you an educated look into selecting the model for you.
Here are a few bits of information to keep in mind:
Filtered and moderated models (externally moderated models), such as models by OpenAI (GPT) and Anthropic (Claude), are not designed to be NSFW models. Whilst the Claude 3 (beta) models don't have external moderation, they will refuse to write if you go too far.
There are also some other models with internal moderation, including gemini and some mistral models. This isn't often disclosed, however you might see the model refusing to write, or not giving you the NSFW content that you desired.
OpenRouter has a comprehensive list of its models (Docs | OpenRouter) and identifies which models are unfiltered. Models are added frequently, so check back to see if there is a new favourite in the community.
Recent models that are community are enjoying (April 2024) are:
Goliath
lzlv 70B
The Novelcrafter discord #models and #romance-explicit-NSFW channels may provide additional insights regarding models and settings.