Currently i'd say for winning a playthrough it would take about an hour? (Reminder i'm biased I play the game over & over so I'm kinda guessing xd)
I want each chapter to be about an hour long to complete (45m to 1h), but if you wanna complete the whole gallery it might take additional time expect an hour & a half or so.
And dom/sub scenarios are already in the game, path is a big word I wouldn't say there's a dom or sub path yet? It's more of a neutral ending to the current scenario but that'll change and surely have a few endings to it including dom/sub paths :)
And romance is still on the table I just am not sure how to include it and it would bring another big amount of work so i'll see about it later :) (If you don't count Lumi as romance tbh)