I think if you're using the "Collected by Itch.io" method, most of your questions/concerns don't matter. People who buy your game will pay either through PayPal or Stripe, and the money will go to Itch.io (in the US). Then, after 7 days, you'll be able to transfer the money to your own PayPal account. The country you (the developer) are located in will affect the amount of taxes/fees you pay, but besides that I don't think it will matter since Itch.io is the Merchant of Record.