Early medieval Germany was comprised of independent city-states. Their only unifying factor was a set of cultural and linguistic practices. So, in regards to the German contribution of Arthurian ideas, it is Perceval, the Holy Grail, and the Tristen legend which receive the most attention by German authors.
The principal authors in the Arthurian German tradition is Harkman Von Airyah, Wolfvon Bon Eschbach, and Gotfried Von Strasberg. If we are to talk about which ones are more important than the others, then the order would be the following:
Harkman: researchers believe that he was probably a knight. During the period in which German writers took an interest in the Arthurian tradition, knighthood was becoming an integral part of how the city-states founded their social identity based on aristocratic violence. So Harkman’s text’s inclusion of knighthood is unsurprising. Harkman’s efforts were to rework “Eric and Eneed” into a parable of finding balance between domestic life, Romance and knighthood in relation to God. Harkman takes stories at only hinted at in Chretien de Troye’s original writings and expands them into full-fledged stories.
Wolfvon: the most important of the German writers, his treatment of Perceval ignited a German obsession with the Holy Grail, something which reflects a literary awareness on part of the German city-states. Prof. Dorsey Armstrong suggests that Wolfvon was even the “medieval Joyce” for his literary brilliance and conceited attitude. If one was to give a title to Wolfvon’s treatment of Perceval it would be, as Armstrong says, “a brave man slowly wise.” Indeed, neither of these claims are absurd since Wolfvon’s text is widely considered one of the three most important medieval texts during this period in the German tradition.
Some of the changes are: the Holy Grail isn’t a cup, but rather a stone. It becomes associated with immortality and life. The Fisher King, meanwhile, is altered to indicate a knight-leader who broke code and became wounded, but cannot die because of his close association to the grail. Additionally, the question which would heal the king is more logical—“Sir, what ails you?” Wolfvon also adds thousands of lines of backstory and Gawain-Perceval back and forth while also finishing the Gawain and Perceval story itself.
(Gotfried, meanwhile, is only an indicator of importance; his tales had some Arthurian value but were more of an initial introduction)