Where do customers see my bank account details after placing a Bank Transfer order?

On the order confirmation page. Right after checkout, a box headed "Complete your payment by bank transfer" shows the details you saved and asks the customer to use their order number as the transfer reference.

The box shows the account name, account number, IFSC / Routing code, bank name and branch, and the SWIFT / BIC code if you filled it in, followed by your Instructions.

Edit these in Settings → Store Settings → Payment Gateway with Configure on Bank Transfer, and click Save Changes. Use Instructions for anything extra, such as how soon you confirm payments.