please clarify what you mean by "harvesting gains"?
if you are entering a 1099B to reflect capital gains from a non-qualified account, it is taxed at the capital gains rate (15% for many taxpayers).
if you distributing money from the Trad IRA as either a Roth conversion or just taking the money, that is taxed as ordinary income. This transaction would be reflected on a 1099-R.
both entries add the same income to your MAGI calculation to determine any IRMAA impacts, but the income is taxed at different rates.
