I have had Weathertech side window deflectors on several car (Hondas, Dodge Caravan, VW Golf...). They fit into nicely into the window channel, no tape required. Personally I like the look and the ability have have the window open a bit without buffeting my head & reducing heat build up on hot days. With the windows down an inch or so, it is not noticable to casual passer bys. Personally have used them only on front windows and I like the look. I feel they have been a nice, solid addition to past cars.
Just looked on WeatherTech and they currently don't have any for Niros.