I found as Sebille better as a main character over companion. "Conflicts" that posters here mention go away because you control her actions.

Storywise, I like that she's constantly forced into situations while trying to maintain her freedom. That applies to her personal story and being forced into Divinity by a God she hates. She pairs up well with Ifan as their both mercs and have a connection to elfs. Red Prince is also a good pairing. Corpse Eater can add good tidbits to the story.

Fane and Lohse are great as both mains and companions. Beast seemed like he has the least amount of story content, tried him after DE and didn't notice a big difference.