If you were legally married at the end of 2020, you cannot file as Single.  You can file as MFJ (if both agree), Married Filing Separate (gives you less credits & could have you pay more taxes), or if you qualify Head of Household.

If you want to file differently from last year, then do not use your Joint account.  You would need to start a new return. No information from your joint return will transfer to your new account.  Any 2019 information needed, you would have to manually enter the information.

Can a married person claim Head of Household filing status?

https://ttlc.intuit.com/community/married/help/can-a-married-person-claim-head-of-household-filing-s...

More information, see the following:

Is it better for a married couple to file jointly or separately?

https://ttlc.intuit.com/community/married/help/is-it-better-for-a-married-couple-to-file-jointly-or-...

How do I start another return in TurboTax Online?

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-onli...