Changing your 2019 return won't change any stimulus checks. The Stimulus Check is really based on 2020 tax return. Any amount you already got will be reconciled on your 2020 return line 30. If you didn't get a Stimulus Check (and qualify) or you qualify for more it will be added to your 2020 return. But the good news is if they paid you too much they won't take it back.
When you go through the federal review tab it will ask how much you got if any. Or to enter your stimulus payment in TurboTax, type "stimulus" (without the quotes) in the Search box, then click the link that says "Jump to stimulus."
@VolvoGirl do you know when TurboTax is going to update the system for 2021? We already have all of our information on file for 2020 just waiting to be able to file it and it does ask about the stimulus but I am assuming it is referring to the first stimulus not the the second because it has not updated the amount. We were late filers and had to mail in our return, just this week. I assume it is going to take a few months to process so we were worried we weren’t going to get a second stimulus either..as of today TurboTax has not updated to where it asks “did you receive stimulus” effecting the new stimulus just the first. Does that make sense?