This feature will only be relevant for organizations processing supporter bank account and bank transit numbers (sort code) in order to set up recurring donations (e.g. BACS type payments such as ACH and Direct Debits).
It is expected that several US states will pass laws to make it illegal to store bank account numbers and transit numbers. Therefore, after April 4th you will have the option not to store this data. This setting will be managed via your Account Preferences page. Superadmins can go to this page via the Hello menu at the top, Account settings then Account Preferences.
Choosing to not to store this data in your account will also trigger a process to clear any stored data already in these fields.
Any integrations with gateways would be unaffected by this setting, and the data will be sent securely exactly as it is now. Recurring payments are tokenized and we do not need to store this data. However, if you need this information to set up BACS payments manually by using exported data, then of course you should not tick this setting.