My two cents.
I got the 20" Clearview and it works fine. I'm 6'3" tall so I need the taller screen. My first purchase was the 18.5" Clearview and that was definitely too short for my height. The wind buffet on the top of my helmet was worse than no screen at all.
I normally look over the top of the screen, but can see the road clearly when looking through the screen.
The Clearview quality is excellent. One of my complaints though is that the mounting holes do not perfectly align with the Triumph mounting kit brackets (upper fixing kit). The lower brackets and holes fit perfectly; however, the top holes on the screen don't. It appears that the screen curvature is slightly different which causes a small misalignment between the top brackets and the screen. Not a major deal, but I've been watching for signs of any cracks...so far so good.
The other complaint is that it take 2 to 3 months to get a screen. Perhaps now that is winter in the upper hemisphere, the wait time will be less.
Lee