You do lose out on scenes with the main girl if you pursue side girls but the story is still advancing anyways. No clue about the endings yet but considering how it's handled so far it's safe to say they'll be affected as well. And being 100% honest with you there isn't anything extra even if...
The short story it's based on which you can view in game by clicking "Original Story" has the ending of the career path. I think the family ending is an alternate what if. I also wondered the same but Sandra could use some more happiness in her life so whatever.
The original story's ending...
Man this really sucked, I was pretty invested into the characters too. Second time this Dev let's me down so I can't wait till he fucks up All The Wrong Things too.
I just installed the game and DLC's today, both on 20b. Turned off PC and came back to continue playing and my old saves don't work anymore. What is the joke, that I have to start a new playthrough each time?
Edit: fixed the issue, looks like it's the CCB DLC that was repeatedly causing this...