@purpleblob1; @Redglyph; I found this explanation of combat death from a LA developer on their discord:
"Characters that go down to 0 hp will bleed out if you have Combat Death enabled. After 3 turns they will die if they are not stabilized by a skill (such as Aid, Cure, Bandage). If the character is a companion or the player character; it will prompt a game over.
However after Lesbos; Injury system gets enabled, which means getting damaged/downed can trigger injuries that needs to be treated."
Hmm, it's still somewhat unclear for the injury system, could companions die that way without the Combat Death option? Or do you only have to treat them so they can fight again?
They seem to be smart, I doubt they'd end up with an incoherent system, so I think that if you don't select that option, you're safe and there's no game over because of combats or their consequences.
Anyway, the best option is to save regularly, we'll see how this all works in due time.
EDIT:
"We don't have that many quests in the game where you have to bring the companions - and we have lines written for the hired praetorians if you bring them instead."
That's nice.