I think the genre you are looking for is “immersive sims”. Notable historical examples are Thief, Deus Ex, and System Shock.

Ultimately, these sorts of crimes are incredibly common for occupying armies. Culture impacts the way these crimes are handled – are they punished, ignored, covered up, or tacitly (or even explicitly) encouraged? But the common element is soldiers, and the way that war leads to the dehumanization of the enemy, not that some cultures breed uniquely evil people.

I generally have a few “forever games” that I sink thousands of hours into. Right now that’s Stellaris but in might try to get back into Crusader Kings with the new patch and of course when Civ 7 comes out I’ll be all over that.

I generally prefer my other games to be fairly short, especially for story heavy games. I’ve left hundreds of Civ games unfinished, and it doesn’t really matter, but I do actually want to finish games with a strong narrative, and really long ones can be hard. I never finished either of the Divinity original sin games, for instance, despite enjoying then quite a lot. Same with Witcher 3, though in that case it has more to do with rapidly becoming fatigued with the open world and also starting grad school about 3/4 if the way through and not having much time to play. I’m general though, I’d say about 20-30 hours is ideal for a game that I can’t just replay forever.