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, you cannot use SCSS variables in your codebase inside the Acquia Cohesion interface.
To use an SCSS variable, enter your chosen variable into the appropriate CSS property.
No, the entity browser does not work for component defaults as the entities are content, not config.
Yes, this is possible by creating a custom element.