As someone who has played the game many many many times I feel qualified to answer this. Altho I am not part of the project or anything like that, just another fan. So this is all just IMO.
It's mostly what is your relationship like with Cove at the end. Like you can be anything from just former neighbors who don't really talk all the way to a married couple and many things in-between.
You can love Cove and never admit it or never like Cove and admit it during stage 2, 3 or 4. Or just be friends or best friends or almost family without having to fall in love or have a crush. If you do have a crush or fall in love, when you admit it (or if Cove is the one to confront the issue) all changes the story. Also what events you do or don't do etc impact what Cove will talk about, say, feel etc.
Also Cove can end up being super shy or not so shy or somewhere in between. He can be athletic or studious or some mix of the two. These are things you can set at each stage to override things or you can let this all be based on the choices you make.
They really let the player control the narrative and its really cool IMO.
You should replay a few times :)