While it's true that adding sugar will bump the alcohol content, you are wise to be concerned with balance. The mist kits are designed to balance acid, sugar, alcohol, and flavor. Once you start tweaking, you need to be prepared for the results. Harvey obviously was able to rely on his knowledge (maybe some from trial and error) to hit a product you liked. Here is what I tell new winemakers who take my classes. Make a few kits following the instructions as written. The wine may not be the perfect wine for your tastes, but if you follow the instructions, it will be a nice wine that people can drink and enjoy. After you have some bottles done that everyone can enjoy, then start playing the part of the mad scientist. You will have some wines that turn out nice and you can be extra proud because they are your creation, but let me caution you; you'll also have wines that aren't all that great. You might end up dumping them, or while drinkable, you wouldn't serve them to friends. All home winemakers who have made wines from scratch have some batches they're not fond of. They may still drink them alone in the dark, but they don't pull them out when company comes. If you make a wine to the kit specifications, you're sure to have some wines available when company comes even if your experimental batches don't turn out the way you planned. Cheers, good luck, and above all, have fun.