If it's something like The Sims, I behave as deliberately chaotic evil as possible, because that's how I have fun in simulator games. And sandbox games. And games I don't really care about.

But if it's a game with genuinely good writing and complexity, I tend to just follow my personal beliefs about the subject in question. There are a lot of choices in games that have stuck with me, but in terms of actual ethical dilemmas, none have left me as anxious as SOMA and its repeated interrogation of things like self-awareness, the right to life, and the blurry line between cruelty and mercy.

As for following a character opposing our beliefs or agreeing with the antagonist, I usually don't have any problem with that (being forced to do things that make my stomach turn often makes for some of my favorite moments in gaming) unless the story itself is trying to tell us we should agree or disagree with the ones we don't. That's the difference between playing, say, a Yoko Taro game -- where the protagonist and antagonist are often on very dark shades of gray and almost no one is ultimately on the right side of history -- and playing a more traditional JRPG that expects you to hate the villain as a matter of course and excuse any questionable actions the plucky young protagonists have made.