For example in games like hitman the gameplay isn't based on saves but on playthroughs vs cyberpunk which Is based on the saves. Like with cyberpunk you can join a completely different game through the saves but with hitman the saves just put you somewhere in the level. So I was just wondering if the games data would save or just the saves? And if it is just saves how are games like hitman saved?
As far as I can see for each game save you get a .json file and a zip file in which your save game is.
But best in your case for Hitman is probably if you perform a download of your Stadia data yourself. It's quite simple, you request it and then get an email with the link once it's ready and then you can download it as a zip file. More info you can find here: How to download your Google data