@EllieBucket The "unrecognized video card" message means your graphics card's device ID isn't in the game's database. It's not a problem as long as you're not seeing any graphical irregularities, which you haven't mentioned. The message only pops up the first time you launch Sims 4, or the first time after you move the user folder—the data that says you've already seen the message is stored in Options.ini inside that Sims 4 folder.
Anyway, if the new save is running fine, you don't need to try the other steps yet. Instead, copy one of your existing saves from the old Sims 4 folder to the new one and test that, with no other content present. Since you're copying rather than moving the save, you don't need to worry about the effects of any missing mods or custom content; the old save will be intact in the old folder while you experiment on the new copy.