For both Lancelot and Lady Lyonesse, she will find the same as stated for this realm's version of Gareth that they lived their lives as stated in the lore. The same for the Red Lands there is the story of the Red Knight from the Red lands but not much else. As for the Grail, all that will be found is what is stated in the previous response about the Fisher King and that there are many different accounts as to where the Grail finally ended up.