Welcome to ECF.
I have to admit, I had to Google what veppo vetta was. Look like they should be nice batteries. Although they claim they are better than Ego brand, I have a suspecion that they are just a rebranded ego. Doesn't matter, Egos are a nice battery.
You actually started smoking at age 8?!

Heavens!
To get back on track to your question, Tnt answered well. Instead of being limited to the regulated output of your battery's 3.7v, a variable voltage APV uses a boost circuit to increase the voltage given to the heating coils. It's not just about more vapor or hotter vapor.
Some juices have better flavor production at different voltages. Say for instance, fruit flavors are delicate, and are best vaped between say 3.4 and 3.7v . My favorite coffee flavors taste best between 4.4 and 5.ov . So, as Tnt pointed out, each juice as a "sweet spot" that variable voltage allows individual vapors find for each juice.
There's much more to learn here. Take off your shoes, pull up a chair, and get your vape on here as you go over all the information. There's a lot of knowledgeable and helpful people here to help you with the overwhelming amount of information.