you can change the a/c until you file the 2020 return. the earliest it can be filed will likely be late January 2021 when the IRS opens for e-filing. as of now its likely the IRS will use the same a/c as it did for the original EIP. if that's closed the deposit will go back to the IRS so a paper check can be issued. it will go to the last address the IRS has. if it changed you need to file form 8822 with the IRS and change of address with the USPS
you can not change your bank information for the stimulus payment. It can only be changed when you file your 2020 tax return. Here is the IRS FAQ:
No. To help protect against potential fraud, the tool does not allow people to change direct deposit information already on file with the IRS.
If we issue a direct deposit and the bank information is invalid or the bank account has been closed, the bank will reject the deposit. We will then mail your Payment as soon as possible to the address we have on file for you, and we will update Get My Payment to reflect the date your payment will be mailed. Typically, once the payment is mailed, it will take up to 14 days to receive the payment, standard mailing time.