Making this type of kit without adding sugar will produce a wine with a starting SG of 1.050-1.060 and a potential ABV of 7-8 %. This is the intention of the style to be a easy drinking, no aging wine cooler type of drink.
Adding extra sugar increases the ABV not the final sweetness level since this is a function of the F-Pack added after the fermentation is complete and the wine is stabilized. I am sure the added alcohol does change the wine some but I have never done a side by side comparison.
Edited by: masta