Hello. I just binge read and finished Mother of Learning and The Metaworld Chronicles. I loved it and want more. Many mentions for Wandering Inn and Practical Guide to Evil, so I have that on my next reading list. But I am craving for a fantasy or maybe a scifi-fantasy (prefferably with a female protagonist) and a romantic subplot or at least a smidge romance. I have been prowling the rrl site to search for something with a good story with reasonable romantic subplot with smut, but aside from Andur, I'm having a hard time searching. If you know other sites that has some good original fictions, please do let me know. YES to: 1. Good and complex world building 2. Interesting and relatable characters 3. I like a bit of mystery to the story 4. Bonus if there is smut or nsfw. NO to: 1. Ntr 2. Harem/reverse harem 3. No short story please 4. No goblins, or ugly monster and other abberant romantic interest please.
Check out He Who Fights With Monsters I have found it to be very enjoyable. It does not fit all of your criteria but I have really enjoyed the story so far.
Lament of the fallen (finished) Azarinth healer (in progress) Song of the void (in progress) All on rrl 1 & 2 are fantasy 3 is sci-fi
A Tail’s Misfortune. Azarinth Healer. Binary Soul. (Completed) Forgotten. I Am Goint To Die (In This Game-Like Dimension). Lament of the Fallen. (Completed) Lily Ex Machina. (Completed) Quod Olim Erat. Song of the Void. Substitute Hero. (In creative novels) Suddenly, a Succubus. (Complete) Taint. (In black blood tales) The Demonologues. The New Journey of an Old Soul. (Completed) To Play With Magic - A Forerunner Initiative Story. Trouble With Horns. (In scribble hub) Undermind.
First story that fits all of your criteria: The Demon Lord's Lover by redknight3996. Seems perfect for you honestly. Also good besides the lack of significant mystery: The Empress of Blue Mountain followed by The Emperor of Blue Flower Mountain by Queenofthefuzzybugs. Finally, for two great stories with female protagonists, but do have a lack of romance, check out The Twilight Kingdom by Jemima and A Journey of Black and Red by Mecanimus.
If you don't mind overpowered MCs and reincarnation then: Second Chances (litrpg & scifi/fantasy mix) Gray Mage (urban fantasy, but not exactly "modern") Not sure if these are up to ur standards in comparison to Metaworld Chronicles but u might still like them. Most of the stuff I can think of has already been recommended lol.
Not on RRL, but self-published on their own site: https://honyakusite.wordpress.com/ None of these have "Yes" 4, though. Fluvia Dellarose was an Otome Game's Villain. Fit's 1,2 & 3 "Yes". MC is currently a child, so not much on the romance side. MC was a single mother, who reincarnated as a side character her daughter was obsessed with due to only having one or two lines in the game (despite taking the blame for the central Villainess's "Crimes" against the game's protagonist, and being executed for learning an illegal form of magic). The game in question had plot threads that went nowhere, and all sorts of things that made speculators and fan fiction writers fascinated, and thus developed a cult classic type following. MC never played, but knows just enough to avoid the one major pitfall her character fell into in the past. Origionstory the VRMMO: The Advent of Axebear. MC is a fit, shapely female who plays a VRMMO as an axe-wielder. Actually, that's the entirety of the basis of the story, but it fit's "Yes" 1 & 2. Not really any mystery, nor anything beyond a hint of romance. Wizard with the Flower Blades. MC is genderbent to female and isekai'd while setting up a character for a VRMMO. MC seems to regularly forget about the gender change, however, and continues living as if nothing about himself has changed. "Yes" 1 & 3, with MC being the main exception to 2 (MC does not really seem to be affected by the world around them on a personal level, even their gender-bending being something they regularly forget).
All-time favorite from RRL: The New Journey of an Old Soul Questionably male MC reincarnates into a female body, so the gender is pretty fluid I guess? Bonus points for nsfw chapters