Yeah, same reason mine is going SFW on release. I'll have an addon mod after release to change it to nsfw. If I put it as a mod steams will conk my account as an nsfw dev. So it'll be 3rd party for sure.
As for steam, I'd recommend putting it out asap just to get wishlists for it. Of course, you do whatever suits you best, but there's no limit to how long you can have a game in wishlist mode. Plus the longer it goes the more it spreads. I think steam recommends at least 10k wishlists before you release.
It also helps you do well in the one time chance at steam Next Fest.
Either way I'm stoked for this and looking forward to new updates. Soon as it hits steam it'll be on my wishlist.