As per the 2020 f4848 instructions:

You don’t need to file Form 4868 if you make a payment using our electronic payment options. The IRS will automatically process an extension of time to file when you pay part or all of your estimated income tax electronically.

TP will pay his estimated of tax liability for 2020 via IRS Direct Pay. Is there any harm to also e-file f4868 via PTO? TP wants to make sure that the extension is accepted and he will not receive any notices.

Also, in order for f4848 to be valid, the IRS Direct pay has to be made on or before June 15, 2021 (TP is abroad). Correct?

Thanks for your comment and time.