How does it work exactly, since I believe someone told me I might be forced to pay more or just the difference once the game updates and the price is higher?
So, as far as I know, you don't need to pay more if the game price remains the same. Itch remembers the amount of money you've payed. The price for the game will be the same for the next update.
Well after steam it would take some getting used to paying more later in chase the price raises, but it's good knowing that thank you. Well no problem I guess.