It depends on what you are going to do with the pictures. E100G is a fairly standard film in terms of contrast and color. It would be a better choice for scanning IMO, as it will render things with more detail and less contrast, which you can later change when preparing the digital file for printing. That can all be discussed at DPUG dot org.
But if you want to project or show the transparencies directly to people, and you want high saturation, then I would shoot the E100VS.
You also are on the right track with your G in contrasty light and VS in flatter light ideas.
If you want to print Ilfochromes, I would also go with the lower contrast and lower saturation film unless you really want extreme saturation.
In any case, filtering in camera on overcast days would generally be a good move when shooting transparencies. Depending on what you want, one of the 81 series filters is a good general starting place. When shooting color landscapes, I always try to have an 81A and an 81C on hand.