I played through the whole game with my gf and didn’t see nor read anything that would indicate that.

Regardless of if you play, solo or with up to 4 people there are 4 characters in your party. Your main character can be one of the predefined ones or not. You will probably have/want a mix of both.

First play through will take more than 100h and you will still have plenty to see for subsequent playtroughs. It’s literally impossible to see all of it first time regardless of how you play.

Just get it, it’s not just a GOTY, it’s one of the best games in a long while.