Types of light diffusion.

Milk – Opalin diffuser
Diffusion, it allows you to do signage. You do not see the LEDs

Frost – 50% diffusing
Ambient lighting. It allows to diffuse the light. (if the profile chosen is deep enough)

Crystal – Transparent
For lighting, it protects the LEDs.
The use of cover will attenuate the brightness of the ribbon depending on the opacity of the latter.