Get your taxes done using TurboTax

I am trying to file 2019 tax year and 2020 tax year.  If I have to mail the 2019 returns to the IRS, can I file the 2020 returns today electronically or do I need to wait until the 2019 have been accepted or processed before I can file my 2020 return?  Would I then need to file an extension for my 2020 tax year?