Have flown VS Y as KFEG. They give you access to the CH, and IIRC (though I don’t see why this shouldn’t be the case), additional 20 kg of check-in luggage, as indicated on the SQ website.

I don’t know if flying an economy light fare affects anything. I suppose you’ll have to check with VS if they do something similar to LH, whose basic fares come with no check-in luggage, even if you are *G. I suspect this is not the case, though.