@Nullo Time travel metaphors are not really about time travel. They are about what-if, mostly. And attempt to work out paradoxes is just a hopeless attempt to twist your mind into places it won’t go.
The question is whether the two people are the same person or a different person. Clones, of course, are different people, just as twins are. So that metaphor doesn’t put us into any different scenario than we are already in. There is only a problem when the two people are actually the same person. But if they are the same person, doesn’t the trailing person have no freedom to do whatever they want? They have to do what they have already done, which is exactly the same thing as what their future self has done.
So, if they are the same person, then the issue is moot because the trailing self has no freedom of action. If they are independent people, then the rules governing independent people are in effect. These are, of course, the rules we live under now.
I guess you are asking us to imagine a situation where we are both the same person and a different person at the same time. Thus actions in your past can change. Things that you remember doing are no longer what you remember doing. A new memory takes its place. Most authors I’ve read let their characters have some dimming memory of the original past, so they can start to try to do something about it. But you could choose any condition from absolutely instantaneous change in memories with no residue of another past to having two sets of true memories about the same past.
Can retrospective past actions change a future that has already happened? Is that a sentence that can make sense in any universe at all? God. What a question. I think I need to ask it. It’s just so absurd.