20% is as high as you'll get ,and that's with champagne yeast, and careful nutrient additions (and feedign honey) to keep it going.
Most meads are going to fall between 12-18% ABV.
the lower end would be more like your dessert meads...lots of sweetness, and a low attenuating yeast used.
there's room for a lot of variation in the style.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10