Does a unique collection give 4 or 7 points?
It only gives 4 points for being unique. Unfortunately, the English version of the rules dropped the nice scoring example in the German version of the rules.


  Ronja: 8 Punkte - Niemand außer Ronja besitzt Masken. Das bringt ihr 4 Punkte ein. Bei den Statuen geht sie - wie Max - leer aus. Auch bei den Zahnketten bekommt sie keine Punkte, denn Max und Lea besitzen mehr davon. 4 Punkte bringt Ronja ihre konkurrenzlose Hutsammlung.


Roughly, this translates to. Ronja 8 points. No one but Ronja owns Masks. That brings her 4 points. As with Max, the statues score her nothing. Also, for the necklaces she scores no points, because Max and Lea have more of them. 4 points for Ronja's unrivaled collection of hats.

It is clear from the images in the rulebook, that Ronja is the only player with Dark Green Mask cards, and Yellow Hat cards. Since she only scored 4 + 4 = 8 for her two unique collections, you don't score those sets for longest of that type as well.