The game can be very strange about re-using Saves, even when your set-up is seemingly identical. It works sometimes, other times not. Some points about the game though... One of the odd things about it is matching the video stream throughout. This involves what the "native" resolution of your monitor is. The old CRT monitors even had a native resolution, such as 1280x1024. Modern LCD monitors can display much wider, such as my current desktop of 1920x1080 for a 16:9 ratio. Other monitors of course, can do wider and more fine, such as 4k and above. The "native" resolution is generally referred to as "recommended" by windows now. So set your Windows desktop to that, and set the game to that from the main menu "Options" "Graphic Settings" and the drop-down box. You might have to reduce some of the other display settings, but most of the newer computers can handle those set higher. Next, if you have Windows 10, make certain the OS is updated before you begin playing, so that the updater doesn't start a download process in the middle of your game. You might also make certain you don't have too much background activity from other processes, such as you get if you have an HP laptop, and they start Support Assistant and other processes every time you boot the computer.
The Steam process is basically a re-install, in that any file found missing, or not dated properly is replaced. If you happen to have a mod enabled, Steam will basically wipe it out. Once you have done that, try to play the game prior to bringing the old Saves back in, and see what it does. If it seems better, then you could attempt to use old Saves, but bring the entire folder back in. You might have to adjust your gameplay settings after doing that... If it fails, do the Steam verification again, wipe the Save folder, and just start over, not re-using the old Saves.
