On the topic of what impact there can be when characters (or players) don't work well together, I have some recent experience with this. I know and play with a pretty wide network of players and DMs via Roll20, some of whom I know better than others.
As circumstances would have it, I was put on the spot to run a one-shot (three-session) adventure for a group. Some of those players were also players or DM in a game that I joined as a player. It became apparent right away in the game in which I was playing that one of the players just wasn't going with the flow. His standard position seemed to be "Whatever the rest of the party wants, I will set myself in opposition." This made everything, including engaging with the module's content, a debate where we had to convince the guy to, you know, be an adventurer. A couple sessions in, I started just saying the opposite of what I really wanted and, sure enough, this guy would do the opposite of that, which was what I wanted to begin with. SIGH. I quit that game. Convincing fellow adventurers to adventure just isn't my jam, even if the reverse psychology was hilariously effective.
Meanwhile, this guy is a player in the one-shot I'm running. The same behavior continues, but with a different character. What the party wants, he does not want, and so the debates convincing him to do this or that continues. I serve up all manner of opportunities for him to do things and he resists or avoid them. It is an incredibly perplexing behavior. I'm glad there's only one session left. If this were an ongoing campaign that he found his way into, I'd most certainly address his behavior with him and give him an opportunity to amend it. Failing that, he'd have to go. What's more, I'm sure he thinks he's a brilliant roleplayer and just "doing what my character would do." And while that's fair enough, doing what you think your character would do must be, as I see it, tempered by the metagame assumptions that make the game function well.
Looping it back to the OP, it's very important to get this stuff out in the open at the beginning of the campaign in my view. If you don't, you risk situations like the above.