I notice there is no Harem tag, how the Hell am I supposed to not go after everyone? I mean I like Bella as Best Girl, but there are so many lovelies!!
Ocean dislikes harem styles, so there won't be a harem. If you go full Nika=manwhore chasing every skirt, there is a chance all the girls will dislike him as untrustworthy. Each path also reveals plot elements that aren't available on other paths, as each girl has a different knowledge of events, so you have to play wisely.
My advice, decide who feels like the most authentic choice for you and play that path. Then make a new save and follow another path. Walkthroughts won't help 100% because Ocean tries to disguise the variables so people are forced to make choices.
That's just the logic of the game.
Also, for the throuple paths, we don't know when they'll be implemented, or what choices are important to make them available. But we do know they will be difficult to manage and the LI's will get jealous.