Do I have to use IMCE?
No. Acquia Cohesion allows the site builder to select, either use of IMCE or Entity browser for browsing and selecting images.
Acquia Cohesion renames to Site Studio from version 6.2. Tell me more.
No, the entity browser does not work for component defaults as the entities are content, not config.
Opacity is set using a decimal where 0 is transparent, 0.5 is 50% and 1 is solid.
Modifiers allow you to apply styles to an element when a specific class, id or attribute is present.