i doubt its teflon, probably a ceramic material if anything. but i would avoid mystery coatings that you dont know what they are made from. if your budget allows the titanium one, thats probably the best out of the list.
as far as the watt density, given those elements are 10" long from the pictures, and folded over 4 times, that is about 36 inches of element (the sides with the terminals arent ful 10" long). if you take a look at this commonly used 5500w element...
Amazon.com: Camco 02933 5500W 240V 14-Inch Screw in Lime Life Foldback Water Heater Element: Home Improvement
14" from base to tip, and the fold doesnt come all the way back to the base, so im going to estiamte that to be 11-12 inches. so if unfolded, that is around 50 inches of element. thats considerably longer than your element for the same wattage. even though its 50 inches long, some people do experience scorching with this element.
depending on the actual thickness (which isnt given), and thus, surface area, you might have a harder time avoiding scorching than with other actual low watt density elements. at the very least, you will end up with darker beer than you would using ULWD elements or direct-fire, simply due to much more maillard reactions. that isnt necessarily bad, but should be kept in mind.