we can not see the effect if any, the changes in the items you mentioned would have on your 2020 return. in some cases, there may be changes that will result in an additional refund or you'll owe additional taxes. so you need to prepare an amended 2020 return making only the changes noted to the w-2 to see. if no changes then I would not file.
since the payment occurred in 2020 and the repayment occurred in 2021 you have 2 options since the amount repaid (really for tax purpose $20k the net you repaid
Repayment
1) you can take as a deduction on Schedule A line 16 denote as IRC 1341 repayment OR
2) recompute the taxes FOR 2020 BY REDUCING BOX 1 WAGES BY $20k. The decrease in taxes is taken ON YOUR 2021 RETURN as a credit on schedule 3 line 12d denote as IRC 1341
