When you transfer information from the previous year, TurboTax does not transfer the dollar amounts for income, expenses, and so on. It transfers information that is likely to remain the same from year to year, such as your name and address, employer's names, the name of your business, business code, accounting method, etc. There is no advantage to entering all of this into a 2019 return and transferring it to 2020. Just start your 2020 tax return from scratch and enter everything in the 2020 return.
If you enter 2019 amounts in your 2020 tax return, I would be afraid that you would overlook some things that should be deleted or changed, and end up with an incorrect return. I suggest that it's better to just enter the 2020 amounts as they become available, and avoid any possible confusion.
