If time travel were to exist, which theory would you subscribe to?

Some ideas are:

• You branch off into another timeline and your actions make no difference to the previous timeline
• You’ve already taken said actions but just didn’t know about it so nothing changes
• Actions taken can have an effect (so you could suddenly erase yourself if you killed your parents)
• Only “nexus” or fixed events really matter, the timeline will sort itself out for minor changes
• something else entirely