I disagree with donnachris - the highest I've been from using my vapourizer has been from premium kush, so don't let the quality of weed act as a deterrent.

The temperature you set your vapourizer at is the most important. Mine is set at 180-190 degrees Celsius. The higher the temperature, the harsher and less pure the vapour will become. You will also know if your temperatures are too high if you're burning the weed in the bowl.

I've been using the V-Tower for about 4 years now - it's amazing, and a much more competitive price than other vapourizers on the market (like the Volcano). The V-Tower is well made, is reasonably quiet, and comes with a whole bunch of accessories.

Bags vs whips. I mainly use bags simply because this way I don't have to keep the vape running the entire time when I use my whip. Neither will get you higher than the other because you're inhaling the same vapour.

Hope this info helps.