Hey LordSaber,
sry for the late response. Haven't checked my account for a while.
About your questions:
Solid cubes and outlines cubes have the same point value. They just come from different sources:
Solid Cubes: Head and Special Attacks
Outlined Cubes: Hands
Hitting all cubes is hard, but not impossible. You can also use your head to hit them.
It's not necessary to hit all cubes. You can always go to the next level. After all 3 levels there is a total score and Hank (the man mocking cube) will give you a piece of his mind about your performance (depending on how well you have done).
So feel free to come back and improve your score. Hint: If Hank wants to be your brother, you did a great job! ;)
Best regards