Viognier is a white grape all right, but it is closer in style to a Chardonnay than to a Sauvignon Blanc.
All wines can be operated on - but classically these are the styles that the white wines have:
1) The Sauvignon Blanc - can be as clean lined and crisp as a Sancerre and become fat and a bit ugly like in California, and everything in between. Still the classic lines of a Sauvignon Blanc are crisp clean lines, with intense fruit and floral flavors. If picked early there is more green, if picked too late there is more of a fruit bomb which winemakers turn into a fat wine because of all the sugars - or manipulate it by decreasing the alcohol. It is commonly high in acid and is not meant for a long shelf life - though many a Sancerre have lived long lives - mostly because of the crazy acid and mineral characteristics that come from the Terroir.
2) The Chardonnay is the wine that we all know and can have many different lines. It is a grape which by its nature is screaming to be modified. The grape loses its crispness early on as it ripeness but in its place comes the weight, fruit, and body. The more oak that is applied the more toast, espresso, smoke, and spice flavors get introduced. The grape has less acid as it ripeness but gains more fruit. This is the real quandary with Chardonnay - when do you pick it? When it sits on the vine for too long you get a ton of fruit, little or no acid and high alcohol. To counter act that wineries will dealcoholize the wine and add pH as well. Again - Chardonnay is a grape that is screaming to be managed. However, when done correct you can either get nice green and floral wine with less acidity than Sauv Blanc, but still enough to hold the wine up and enough fruit to carry the day. Or you can make it California style and lose the acid but gain nice weight and body (from the fruit, alcohol, and oak) - but pH added still tastes fake to me.
3) The Viognier grape/wine is a different beast. It is a wine that has distinct characteristics: perfume, floral notes and acidity, but it is a very picky grape. It is very easy to lose to mold and because of this wineries will plant roses next to the grape vines to act as a canary for detecting mildew early on. The grape needs to be picked late otherwise, it does not give the classic perfume that we get from the muscat and Riesling grapes. Depending on if the wine maker puts the wine through malolactic fermentation (to give it a bit more weight) or let the wine lie in the must (to give it more perfume) or to let it have a bit of wood to give it roundness. In the end, the wine is not meant for long storage - hence the VERY early release dates on these wines and the wine should have the acidity, fruit, and perfume to make it a real winner.