Uncapped fps should in theory make no difference - your monitor updates what you're seeing a set number of times per second (it's refresh rate) If vertical sync is setting it to 60 fps, that means your monitor is updating 60 times per second, and your fps being 60 means that all 60 of those times, there is a new frame. It means your computer is experiencing no lag. If it changes a lot, it will seem like lag, even if it's changing from 60 to 400 and back just because the rate at which your monitor is updating can't keep up with what your computer is sending it.
Basically, 60 fps on a 60hz monitor = no lag. If your monitor is actually 144hz, you need to set it to that in windows or nvidia control panel, and vsync should match it.