Windowed mode is always vsynced on Windows 7+ (provided you don't have Aero disabled - which can really only be done on Win7, not on 8 or 10). It doesn't matter what you set in the game. It's actually the only way to run proper triple buffered vsync on Windows. Which is also why it's causing the microstutters - that's something triple buffered vsync can cause.
So running sims windowed is the worst option possible, really - you get the increased input lag of vsync with the added high possibility of microstuttering caused by triple buffering. And you often get worse performance in windowed mode. The only advantage is that you can Alt-Tab reliably, really.