But I'm not entirely clear on a couple things about Carta - specifically, do you/can you backtrack over cards you've already revealed, and if so, what happens?
You absolutely can! Admittedly I should clarify backtracking - thanks!
In the base game there's no rule for it. I would have the card's rules take place whenever you land on a card even if you're backtracking, but for your own game it's up to you!