Yes you can angle the light and that is one of the advantages to them because they focus/highlight certain areas of your tank. To me I enjoy having different intensities of light and even shadows. I have never enjoyed a glass sun box look nor seeing sun spots after looking at someone's tank. There is a thread in another forum and there is talk about how dim tanks look and it seems that some believe that the LEDs are not doing their job because our eyes are not registering "brightness" yet others mention coral bleaching.
Again how many you need will depend on how you scape your rockwork, what you are keeping, and most importantly how it looks to you.