I made a table for this kind of planning ahead. Actually two tables. The first tells you how much a scene is worth in reset bonus. The other, how much a scene will cost you in money and what skills you will need.
Compared to other Idle games there is a big exception (other than this beeing a hybrid with a ladder type challenge game): Higher girls will not give better bonus. Ok, a little bit better, but it slows down to a halt. Girl #20 gives the same bonus as girl #15. As a consequence, for resetting, you will be past any sweet spot if you have to wait several hours for a scene. The bonus of the scene will not compensate you for the waiting time. But as you have noticed, there are other aspects, like training the girls that have to be considered.
Trivia: When the game was rather new you would only get reset bonus for new scenes. And I think when you reset the first time or maybe the first few times, the scenes might be worth a different value. Combined with the anomaly of Lola's scenes, there will be contradictory information in the early pages of the thread. Plus, there might still be a threshold in number of scenes, till the game tells you your expected bonus for resetting.