if I submit two returns, what can I do?

if you e-filed both, the IRS will do a preliminary check on the first one it gets. if it passes you'll get an e-mail saying accepted. The second one will be rejected for duplicate SSN. 

if the one is incorrect but accepted, you have to wait until it is fully processed and then submit an amended return. 

Now you wait.    The IRS will begin to accept or reject returns on January 29.   They will not accept two tax returns from you.   Maybe both of your returns will be rejected, or maybe one will be accepted.   If the IRS accepts one of the returns, then you wait for them to process it fully, and amend later if you need to make corrections.    If both returns are rejected, then pick the one you want to fix, and make corrections to it, then try to e-file it again.  Do nothing else until you get an email telling you if your return was accepted or rejected.

If the IRS accepts the first return you filed, but it has errors, then you will need to submit an amended return to fix the errors after that return has been processed.

There are times when you should amend your return and times when you shouldn't. Here are some common situations that call for an amendment:

• You realized you missed out on claiming a tax deduction or credit.
• You accidentally claimed the wrong tax filing status.
• You need to add or remove a dependent.
• You forgot to claim taxable income on your tax return.
• You realize you claimed an expense, deduction, or credit that you weren't eligible to claim.

See this article and this one for more information on filing an amended return with TurboTax.

See this tool for information about the availability of forms in TurboTax. As of now, Form 1040X for amended returns is projected to become available on February 13, 2025, subject to change.

@ccatv2009