Well if we look at prior work:
Melody let you play around with a lot of LI's but it cost you with Mel and picking certain ones (Amy, Rebecca, Izzy) got you an ending with them and only them
DMD has let you fuck close to a dozen women but your bond with your doughnut is unbreakable
Soo uhhhh errr that's not much help... sorry
I am going to lean on you can mess around and still pick Sis as your one true if it is time for choosing
It might keep you short of the perfect hotel and happily ever after ending but only if it goes like Melody so maybe keep one save Sis only and one save as man-slut