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.
Yes. As long as you are using the Cohesion text format you will see two new menus ‘Element styles’ and ‘Inline styles’. Use these to apply custom styles.
The Youtube video embed is responsive so it should expand to the width of its parent. If you do need to set a width you can apply the Width CSS property through the Style Builder.