how do i amend my 2020 taxes since unemployment payments are now not taxable?

You do not need to amend your 2020 tax return due to the unemployment compensation exclusion.  The IRS will start sending tax refunds in May based on the exclusion.

Go to this IRS website for information - https://www.irs.gov/newsroom/irs-begins-correcting-tax-returns-for-unemployment-compensation-income-exclusion-periodic-payments-to-be-made-may-through-summer

What amount should I expect from IRS from overpayment due to unemployment benefits?