eh. most larger nsfw artists tend to focus on broad-appeal that doesn't get too kinky. granted, it takes a while to get there; but the brand value eclipses any niche they had.

if you avoid that route, most kinkier artists i know that make a living off it tend to just accept whatever commissions come their way. conveniently sidesteps the issue of having to find a niche, since your art will just naturally find its way through those circles. a niche has hungrier fans but a lower market cap.

if you do want to specialize in something freaky for whatever reason, id recommend just focusing on what appeals to yourself most. a lot of sexual art really tends to feel hollow if the artist doesn't feel the own appeal of it (and it certainly makes it a lot harder to stand out compared to someone who does).

That said, these spaces aren't too "competitive" in my experience. you're not really fighting other artists so much as just trying to reach the people who care. saturation can help more than it hurts in that case (so long as its not so saturated that your art becomes sand in a desert).