Use rpgm VX if you like torturting your players, renpy if you foolish belive you are good at writing a story, unity if you want to take the most amount of cpu usage from any computer
Jokes aside you shouldn't bother conforming to any of those standards, and i dont think i've seen someone use unreal engine, porn games are literally begging for an ounce of creativity and a new engine meta would do fucking wonders, assuming someone actually wants to do anything with them