Hey! another reader here. For Bastien's route, I just want to advocate his route and say if you were able to play Guillame's route then you should be able to pull through Bastien's route. Guiilly's route was heavier IMO than Bastien's.
Also, Sir Mathys' route is indeed gonna be on the single route. For the loveless route? it's basically the continuation on the ending in Rose of Segunda where Iolanthe does not romance anyone at Guill's celebration party and basically gets chosen to be the princess by the King in the end.