Benefits of a more aerodynamic vehicle come in the forms of higher speeds, lower ETs and greater stability (tumbling or scraping the wall is bad).

Well, you have a few things working against you in a Bug. First an worst off, the thing is shaped more or less like an air foil...this means lift at higher air speeds. Not optimal. You will feel as a drifty front end (made worse by loose front end parts) and a lifting of the rear when decelerating at high speeds. Another is the flat wind shield but at least only the top half of it really catches the air. Bad thing is the bottom half of the windshield and the part of the hood closest to the the windshield create a low pressure zone and lift on the lightest end of the car.

To counteract the driftiness, guys lower their cars, get the one piece front end with the spoiler that also pushes the air out past the back of the front fenders and cut holes in the backs of all fenders. The spoiler also helps to form a low pressure under the car, the benefits of which are obvious.

Also, the bug front end is more sloped (in the beneficial direction) than a Baja front end to reduce drag. Lowering also reduces drag by reducing the effective frontal area of the vehicle (the car drags the air under the car along with it effectively increasing the frontal area). In a car the size of a Bug, this can mean a reduction of couple square feet of frontal area by lowering 4"-5" by changing tires and suspension. That is very significant and even more so at higher speeds. Lowered vehicles are generally more stable too. It also looks cool.

At the back end, you can put a small spoiler that attaches to the louvers under the back window. The Hot VWs series "Milage Motor" also showed an increase in fuel mileage when using one of these. Increased mileage means less wind drag and potentially lower E.T.s and a higher top speed in the quarter. The really fast cars have a big fabricated engine cover with a big wing on top. Not only is this a nice place to put a turbo, but also helps to smooth out the air flow, disrupt the air foil effect, and further decrease the air pressure under the car. It also looks cool. Another trick is to limit the rear wheel down-travel so when you lift off the throttle at the fast end of the track, the back end stays down and the rear wheels don't tuck (when the rear wheels tuck it also changes the rear wheel toe alignment). This is commonly done with straps or a piece of metal welded on the down-travel stop of the torsion housing.

All of these effects get amplified at higher speeds and are further exaggerated by the fact that wind drag and air foil effects are logarithmic.

That's the basics.