@ArchesNationalPark let me help (a little)
a "CONTRIBTION" to a ROTH is limited as you are aware; it is after-tax money that you decide to contribute to a ROTH; it is NOT coming from a TRAD IRA (except backdoor, but let's not go there).
a "CONVERSION" to a ROTH is coming from a Trad IRA and is not limited (other than by the balance of the TRAD!)
The IRS purposely used those two words related to IRAs because they have different meanings.
most financial advisors suggest that to maximize the value of the Roth CONVERSION, that the tax required to pay on the conversion come from money outside the IRAs ("non-IRA funds"), i.e. other investments you may have. Yes, you can certainly, for example, Covert $10,000 from a TRAD IRA, put $8,000 into the ROTH and use the remaining $2,000 to pay the tax, but financial advisors would encourage coverting the entire $10,000 to the ROth and then finding the $2,000 from other investments that are not in the IRAs - if you can swing it that way.
pleasea read @dmertz comments again 😉
