Nothing that Schwab gives you has anything to do with your 2019 tax return. Your 2019 tax return just needs to include Form 5329 to report the excess contribution made for 2019. Although you could use TurboTax, amending 2019 might be most easily done simply using 2019 Form 1040-X and 2019 Form 5329 downloaded from the IRS.
For 2020 you'll need to amend by entering the code PJ 2021 Form 1099-R that you anticipate receiving near the end of January 2021.
Regarding amending using TurboTax:
https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...
For 2021 you'll already have the code 8J 2021 Form 1099-R by the time you prepare your 2021 tax return.
