Hey, thanks, I’m glad you enjoyed the game! If the goldsink you’re talking about is otherworld exploration, you will continue to get materials and stuff as about the same rate even after you “complete” the activity. That said, it also gets crazy expensive, but the materials might be more valuable than G for NG+. As far as finding storylines and requests and stuff, the wiki for the game has a lot of info: https://outsiderartisan.miraheze.org/wiki/Succubus_Stories
And yeah, there is a decent amount of branching throughout chapter 4 and 5. I am quite proud of how much variability there is! And yeah, saying no to Priscilla really only opens up the other two romance options since she’s first. There’s no particular other benefit to it. I rationalize all player decisions according to the character’s overall personality, and sometimes I think that comes across as suggesting there’s some secret benefit to doing certain things when there isn’t.