I put a TLDR summing up the rest. The takeaway is that these kinds of questions are meaningless, given what we both know and don't know about our universe.
I know some people think of me as some kind of modern day philosopher, but really im just curious about life, and I was thinking today about if time already exists in full and we are just passengers along the line, or if we create it new every day... what do you think gaffers?
Quantum states are total. I.e. all quantum states that are not prohibited - happen. All the time. Which means there's no "you".
After each quantum interaction several new "you" are born each continuing to fork more and more "you" each time. What you feel as your "history" is just one in a billion billions paths that "you" exist in.
All the other "you" feel that their path is the "true" one.
Because of this totality principle and because the sum of all interactions is zero (conservation of energy) the universe spends exactly zero energy into all of "you" timelines.
The fun thing is though. That if you somehow can switch into different timeline, nothing changed. But if you will require your memory of the "previous you" saved, so you will actually remember that you've switched it will require at least whole energy of the whole universe for the duration of your age...